Kinds Of Filaments Research Articles

The catch mechanism of molluscan smooth muscles.

We have examined the arrangements of the thick and thin filaments of the smooth muscle of the adductor of the bivalve Cristaria plicata, Leach, in the catch state induced by acetylcholine, both in ultrathin sections and in separate filaments. The thick filaments are heavily bent and entangled and the thin filaments irregularly arranged. One thin filament may be attached to several thick filaments. When the muscle is in the relaxed state, the two kinds of filaments are seen to be in parallel. However, no difference could be observed in the periodic structure of the paramyosin core of the thick filaments in the relaxed state or in catch. Both cross-striated and checkerboard types coexist. It seems that phase transition is not directly related to catch. We propose that the disordered arrangements of the thick and thin filaments and the formation of three-dimensional anastomosed networks are the structural basis for catch, with a consequent loss of the capability of directional sliding of the filaments and requiring time to restore orderliness.

Ultrastructure of alcoholic hyaline filaments in alcoholic hepatitis.

Ultrastructure of alcoholic hyaline (AH) in alcoholic hepatitis was observed to demonstrate the relationship between AH filaments and intermediate filaments (IFs). Type 1, Type 2 and Type 3 AH were noted in hepatocytes, and the filaments in these types of AH showed similar ultrastructural findings as already reported. Two different kinds of filaments were noted in the Type 2 AH. The large on showed 160 to 200 A in a diameter and the small one showed around 100 A in diameter. Of the 29 cases with alcoholic hepatitis, a new type of AH was noted in the rosette forming hepatocytes in 2 cases of alcoholic hepatitis. The filaments of this AH in rosette forming hepatocytes showed 40 to 60 A in diameter and shorter length compared with Type 2 AH. These filaments with 40 to 60 A diameter were quite different from IFs. Our results indicate that AH in alcoholic hepatitis is not induced by the simple accumulation of the IFs.

Ultrastructural study on the small blood vessels of human vocal cords.

Small blood vessels of human vocal cords were examined by electron microscopy. The endothelial cells contain a large number of filaments. Two kinds of filaments could be differentiated: Short intermediate filaments with a diameter of 10-12 nm, which were localized in the pericaryon, and bundles of thin filaments with a periodicity of 480 nm lying beneath the luminal cellular membrane. The basement membrane of capillaries, arteries, and veins was lamellate. Between the outermost, not fully closed lamellae, myocytes or pericytes could be seen. Both the lamellate basement membranes and the large number of intermediate filaments in the endothelial cells are discussed as stabilizing structures in blood vessels which are exposed to high mechanical forces. The bundles of cross-striated thin filaments may possibly increase the permeability of the vessel wall by their contraction, permitting the well-known fast development of edema in the vocal cords. The importance of Weibel-Palade bodies, which could be disclosed in the endothelial cells in large numbers, is not yet known.

筋肉の働き

The molecular and submolecular mechanism of muscle contraction was surveyed from a crystallographic point of view.The contraction is a result of interactions of two kinds of myofilamants, thick and thin filaments, which are the assemblies of hundreds of myosin and actin molecules, respectively. No conspicuous intramolecular conformational change associated with contraction can be found by X-ray diffraction analysis. What can be detected on contraction is the change in steric relationship between both kinds of filaments. The merits and demerits of electron microscopic and X-ray diffraction techniques in analyzing such changes are discussed. Recent new findings using the technique to reconstruct the three-dimensional structure of such filaments from the electron microscopic images by Fourier transform and synthesis are referred to.

Electron microscopic studies on the myofibrils in the epithelial cells of the Bowman's capsule and of proximal tubules in rat renal cortex (first report).

Two kinds of filaments in parallel arrangement have been observed in the basal part of the cytoplasm in the epithelial cells of a Bowman's capsule and in the epithelial cells of a proximal tubule of a glycerinated rat kidney. The first was thin and linear in shape, 55-70 A in diameter and exhibited arrow-head structures upon treatment with heavy meromyosin (HMM). The other was rod shaped, with thick filaments, 110-130 A in diameter, 0.14-0.16 micrometer in length, few in number scattered among the thin filaments. From the non-glycerinated kidney, bundles of fibers were attached to some electron-dense regions inside the cell membrane. In highly magnified pictures, two kinds of filaments could be observed. One kind was thin, attached to dense regions, and the other thick, and not attached to dense regions. It is conceivable that these filaments correspond to myofibrils from their characteristic electron microscopical features. An electron microscopical analogy detected in both smooth muscle cells and renal cells leads us to speculate that these thin and thick filaments consisted of actin and myosin respectively.

Ultrastructural studies on the formation of myoflilaments and myofibrils in the human embryonic and adult hypertrophied heart.

The myofibrillogenesis in the human embryonic heart is described. The synthesis of thin filaments, which are the first to appear, takes place in close proximity to smooth surfaced SR tubules. Z-band material is closely related to the thin filaments and appears first as irregularly distributed patches in the filamenteous mass. Further cellular differentiation includes an organization of the thin filaments/Z-band material. The synthesis of thick filaments, which follows that of the thin filaments, takes place in ribosome rich areas of the cell. They are rapidly incorporated into the strings of organized thin filaments/Z-band material. The periodic binding sites on both kinds of filaments are believed to play an important role in the precise ordering of the filaments. The formation of myofilaments in the adult hypertrophied human heart is also described. The similarities between this process and that observed in the embryonic heart are striking, and we believe it to be the same process.

Fixation and staining of F-actin and microfilaments using tannic acid

A method employing tannic acid additives in glutaraldehyde fixatives followed by heavy metal postfixation has been used to negatively stain F-actin of muscle and actin-like microfilaments of nonmuscle cells in situ . This technique is potentially useful for ultrastructure research on microfilaments, especially in cases where these structures may be closely associated with, and thus obscured by, other elements of the cell. Analysis of the diameters of different kinds of filaments after fixation with tannic acid has shown that isolated actin filaments and microfilaments of stress fibers in BALB/3T3 fibroblasts appear to have about the same diameter, but they have smaller diameters than thin filaments of muscle. These results have been interpreted as a reflection of the molecular composition of these different kinds of filaments.

An ultramicroscopic study on rigor mortis

Gastrocnemius muscles taken from decapitated mice at various intervals after death and from mice killed by 2,4-dinitrophenol or mono-iodoacetic acid injection to induce rigor mortis soon after death, were observed by electron microscopy. The prominent appearance of many fine cross striations in the myofibrils (occurring about every 400 Å) was considered to be characteristic of rigor mortis. These striations were caused by minute granules studded along the surfaces of both thick and thin filaments and appeared to be the bridges connecting the 2 kinds of filaments and accounted for the hardness and rigidity of the muscle.

Optical diffraction study of muscle fibers

Skeletal muscle fibers act as a one-dimensional grating to electromagnetic waves in the optical frequency range. Results are presented of the optical diffraction study of frog sartorius muscle fibers. 1. 1.|A simple theoretical consideration predicts that, at a sarcomere length near 3 μm, the second-order reflection is contributed only by the thin filaments due to the destructive interference between scattered rays from thick filaments. At that sarcomere length, both the first-order and the third-order reflections are contributed by both kinds of filaments. 2. 2.|Intensity measurements of diffraction lines of muscle fibers at rest at various sarcomere lengths confirmed the validity of our theoretical prediction. 3. 3.|The isometric contraction of skinned fibers was realized by the phoretic injection of Ca 2+ from a micropipette. During the Ca 2+ injection intensity drops of the diffraction lines were observed. At a very narrow range of sarcomere lengths near 3 μm, the intensity drop of the second-order diffraction line became very small on Ca 2+ injection, whereas the intensity drops of both the first-order and the third-order diffraction lines were very large. 4. 4.|A theoretical analysis concludes that the intensity drops on Ca 2+ injection are solely due to small random fluctuations of the position of thick filaments in the sarcomeres.

The cervical lymphatic ducts of the dog: Structure and function of the endothelial lining

In addition to the usual organelles, the endothelial cells of the cervical lymphatic ducts contain numerous fine filaments throughout the central portion of their cytoplasm. The histochemical localization of a myoid fibril stain within the endothelial cells suggests that these filaments are myofilaments which might make the cell capable of some degree of contraction. Fine “anchoring filaments” previously described by others in lymphatic capillaries are observed beneath the endothelium of the cervical collecting ducts. There are two kinds of filament: small filaments and larger filaments that resemble tubules. The abluminal surfaces of the endothelial cells are marked by depressions which could be either pockets or grooves. These depressions are formed by processes of adjacent endothelial cells at some of their junctions and are populated by numerous tubular filaments which have been renamed “junctional filaments.” Although these ducts are among the larger lymph ducts of the dog's body, the smooth muscle cell component is sparse. The paucity of contractile cells and the complete absence of grossly observable spontaneous contractions would indicate that in the cervical ducts of the dog instrinsic lymphatic contraction is not a prime mechanism in the propulsion of lymph. The endothelial lining with its specialized junctions, anchoring filaments and possible presence of myofilaments may, however, play a role in the regulation of lymph flow in this otherwise passive system.

The structural basis of the elastic properties in the flight muscle of the bee

Myofibrils of suspensions prepared from muscles glycerinized in a highly stretched state exhibit striation spacings corresponding to the resting length. This reversibility might have its basis in the fact that the two kinds of filaments do not become separated from each other at the no-overlap point since the myosin filaments begin to stretch slightly below the calculated end of the overlap. These observations confirm our statements in connection with the length-tension diagram of this muscle and with the existence of mechanical connections between the Z-lines and the myosin filaments.

Suggested Changes in "A Revised Classification of the Phylum Protozoa", with Particular Reference to the Position of the Haplosporidans'

The obstacles which have prevented the haplosporidans from fitting into the classification prepared by the Committee on Taxonomy and Taxonomic Problems of the Society of Protozoologists have no objective basis but are essentially semantic in nature. The resemblance between the different kinds of filaments in spores is largely verbal. Therefore, the notion that the presence or absence of a “filament” is the essential character for segregating different groups of sporozoans into subphyla should be rejected. Then, if the subphylum names Sporozoa Leuckart, 1879, and Cnidospora Doflein, 1901, are replaced with the appropriate ones, Rhabdogena Delage and Hérouard, 1896, and Amoebogena Delage and Herouard, 1896, all obstacles to putting the order Haplosporida Caullery and Mesnil, 1899, into a satisfactory position are removed. Likewise, it then becomes logically possible to put the order Paramyxida Chatton, 1911, into the classification. Accordingly, these two orders are placed in subphylum Amoebogena, in classes Microsporea Corliss and Levine, 1963, and Myxosporea Bütschli, 1881, respectively. The latter class, having two groups of orders which are in sharp contrast to each other with respect to structural complexity, is here divided into two subclasses, Myxosporia Bütschli, 1881, (with orders Myxosporida Bütschli, 1881, and Actinomyxida Stole, 1889) and Paramyxia (with orders Paramyxida Chatton, 1911, and Helicosporida Kudo, 1931). It is suggested that the older name Sporozoa Leuckart, 1879, be used (after appropriate change of ending) to replace the class name Telosporea Schaudinn, 1900, and that the latter be discarded.

DEVELOPMENT RESEARCH FOR AN ACRYLIC CONTINUOUS FILAMENT

Using the acrylic continuous filaments prepared by the dry spinning process as described in the previous report (I), cantilever drawing and drawing in steam and by a hot plate were done. Some physical properties of the drawn filaments were measured, also taffeta was woven of the drawn filaments. The acrylic continuous filaments were compared with other kinds of filaments. It has been found that:1. In the stress-strain curves of the cantilever drawing, the region in which drawing tension remains constant is relatively narrow. So, the drawing must be uniform, and the non-uniform drawing accompanied by necking hardly occurs. The tension of drawing under usual condition is lower than those for polyamide and poly (ethylene terephthalate) by one order, and nearly equal to that for poly (vinyl chloride). It is considered that the drawing behavior of polyacrylonitrile is characteristic of atactic vinyl polymers.2. It is possible to draw acrylic continuous filaments in steam at the high speed of 600m/min, but at the speed of only 100m/min by a hot plate. It is practically impossible to draw by means of a hot pin.3. The filament drawn in steam has higher strength and lower elongation. It is a high orientation type, having higher value of shrinkage in boiling water, lower velocity of dyeing and lower number of twist. On the other hand, the filament drawn by a hot plate has lower strength and higher elongation. It is a low orientation type, having the same velocity of dyeing as that of the staple fibre. Although in the drawing by a hot plate both the temperature of heat treatment and the contraction during heat treatment are much larger than those of drawing in steam, the shrinkage in boiling water still survives, indicating poorness of heat-setting property. It may be considered that the poorness of heat-setting property is the characteristic of atactic vinyl polymers.4. The stress-strain curve of the drawn acrylic continuous filament lies between those of poly (ethylene terephthalate), nylon and rayon, acetate.5. Compared with taffetas woven of various filaments, the taffeta of acrylic continuous filament is situated between poly (ethylene terephthalate), nylon and rayon, acetate in strengths and wash and wear property. However, it is distinctively the most excellent in touch and the silkiest of these man-made filaments. In addition to this, crepes are easily woven of acrylic hard twist continuous filament yarn. This is the property poly (ethylene terephthalate) filament does not have Further, dyed with cationic dye, acrylic filament is superior to poly (ethylene terephthalate) and nylon filament in brightness of color.conclusion: Acrylic continuous filament is the most aesthetical synthetic fibre.

STRUCTURE AND FUNCTION IN SMOOTH TONIC MUSCLES OF LAMELLIBRANCH MOLLUSCS.

Muscles like the smooth adductors of lamellibranch molluscs, and the anterior byssus retractor of Mytilus ( ABRM ) possess two remarkable features which have been studied intensively during recent years. They can maintain a steady level of tension (tonic contraction) for longer than any other muscle type (see Marceau 1909), and their contractile apparatus contains, in addition to the usual actomyosin, large quantities of a protein (tropomyosin A—TMA ) apparently not found in vertebrate striated muscle (Bailey 1956; Kominz, Saad & Laki 1957). As in vertebrate striated muscle, the contractile apparatus of these smooth molluscan muscles contains two kinds of filaments, thin ones and thicker ones (Hanson & Lowy 1959; Philpott, Kahlbrock & Szent-Györgyi 1960). In both muscle types the thin filaments are of similar diameter and contain actin; but the diameter of the thick filaments is about ten times greater in the molluscan muscles, and it is these filaments which contain TMA (see Lowy & Hanson 1962). When large quantities of TMA were found in these molluscan muscles, their outstanding capacity for tonic contraction was not unnaturally connected with the presence of that protein (Bailey 1957). A hypothesis was proposed according to which there exist in such muscles two independent systems acting in parallel: the usual actomyosin system which produces tension, and a unique system ( TMA filaments) which, by becoming rigid, can maintain this tension with negligible energy expenditure, after the actomyosin system has relaxed (Rüegg 1958; Johnson, Kahn & Szent-Györgyi 1959). The evidence in support of this ‘independent catch hypothesis’ is based on studies with preparations of TMA , on experiments with glycerol-extracted muscles, and on certain experiments with the living ABRM treated with thiourea. Results obtained from structural studies and from extensive investigations on living tonic molluscan muscles have suggested an alternative hypothesis, the ‘linkage hypothesis’. This holds that, as in vertebrate striated muscle, tension in tonic molluscan muscles is both generated and maintained by the same system, which is one that involves interaction between adjacent actin- and myosin-containing filaments in a sliding filament system (Lowy & Millman 1959 b , 1963).

The contractile mechanism of the anterior byssus retractor muscle ofMytilus edulis

The mechanical properties of the living, isolated anterior byssus retractor muscle ofMytilus(ABRM) have been studied under isometric conditions, and during length changes at constant speed. Stimulation of the muscle produces two distinct types of response, characterized by their tension decay rates. The rate is high in a phasic response produced by repetitive stimulation, and low in a tonic response produced by direct current or acetylcholine (ACh) stimulation. After cessation of contractile activity (i.e. the ability to shorten and develop tension actively), in both phasic and tonic responses the decay of tension becomes exponential. The time constant of tension decay ranges from 1 to 7 s for the phasic response, and from 5 to 100 min for the tonic response. Application of 5 hydroxytryptamine (5HT) to a tonically contracted muscle converts the tonic tension decay rate to the phasic tension decay rate. The resistance of the muscle to extension is greater during tonic than during phasic stimulation, but much the same during and after tonic stimulation. This is interpreted to indicate that the system which is responsible for tonic contraction is in action during tonic stimulation. Nevertheless, there is no difference in either the shortening speed at zero load, or the rate of rise of tension (after a release) during tonic and phasic stimulation; and this is also true for the muscle’s undamped series compliance. In both phasic and tonic contractions, tension is developed actively from 0*2 to 1*5l0, wherel0is defined as the shortest length of the muscle at which resting tension can be detected. Maximum tension is developed nearl0and decreases on either side of this optimum. The shape of the isometric tension-length curves is similar for phasic and tonic (ACh) contractions, but about 20% more tension is usually developed in the latter case. When the unstimulated muscle is slowly extended abovel0two types of tension are produced: (1) true resting tension, probably due to inert elastic material in parallel with the contractile apparatus, and (2) a variable amount of tension identical to passive tension (i.e. the tension remaining after stimulation when the muscle’s ability to shorten and develop tension actively is over). At any particular muscle length, the sum of passive and active tension is nearly the same, although there may be large variations in the amount of passive tension present. In a twitch, as in a tonic response, tension decays slowly, and greatly outlasts the muscle’s ability to shorten and develop tension actively. When the muscle is stimulated with single shocks spaced 10 to 30 s apart, a high level of tension can be developed, and maintained for periods up to 20 h. Such an intermittent activation mechanism may operate vivo during tonic contraction of the smooth retractor and adductor muscles of lamellibranch molluscs, thus enabling tension to be maintained very economically. Tonic tension is, in fact, often maintained in the isolated (stretched abovel0) by `spontaneous ’ contractions occurring about once every 10 s. Each individual contraction, which resembles a twitch, is accompanied by one or more action potentials similar to those observed in twitches, or at the onset of repetitive stimulation. It is suggested that tension in theABRMis developed and maintained by a system similar to that in vertebrate striated muscle, theABRMsystem being specialized in that under certain conditions tension decays extremely slowly. A hypothesis in terms of a sliding filament contractile mechanism is put forward which postulates: (1) that contraction in theABRMis due to linkages formed between two kinds of filaments, and (2) that the breaking rate of these linkages (and thus the rate of tension decay) is governed by the concentration of a relaxant (probably 5HT), the single process of breaking of linkages being reflected by the exponential phase of tension decay. The results are interpreted on this hypothesis, and discussed with reference to another hypothesis (Johnson, Kahn & Szent-Györgyi 1959; Rüegg 1959, 1961a), which holds that in addition to a contractile (actomyosin) system, muscles like theABRMhave a second (paramyosin) system which becomes rigid during tonic contraction, and thus maintains the tension developed by the contractile system.

The structure of the muscle fibres in the translucent part of the adductor of the oyster Crassostrea angulata

The arrangement of the protein filaments and other details of the ultrastructure of the con­tractile apparatus have been studied by methods which include the examination of thin sections in the electron microscope. The results help towards a better understanding of three general problems: the reasons why some muscles appear striated and others smooth; the mechanism of contraction in muscles which are not cross-striated; and the mechanism by which certain muscles of molluscs can maintain a high level of tension for long periods without fatigue. The filaments are of two kinds, thick paramyosin filaments, and much thinner filaments which very probably contain mainly actin. Both are short, relative to the length of the fibre, lie parallel to the fibre axis, and are grouped into separate arrays which alternate with each other along the length of the fibre. The arrays partly overlap, and in the regions of overlap each thick filament is surrounded by twelve thin ones, and each thin filament is usually ‘shared' by two thick ones. The regions of the fibre where the arrays of thin filaments are exposed are identified as I -bands, the intervening regions (arrays of paramyosin filaments partly over­-lapping with arrays of thin filaments) as A -bands. The relative positions of the arrays change with the length of the muscle: the extent of overlap in the A -bands increases as the muscle shortens and decreases on stretching. Thus the muscle shortens by a sliding filament mechanism. Although the muscle is identified as a striated muscle because it has A - and I -bands, it differs from cross -striated muscles in two respects. In the first place, the bands lie at a small angle (about 10°) to the fibre axis, and are arranged helically around the outer part of the fibre, giving rise to the ‘double-oblique striation’ visible in the light microscope; more­ over, the bands branch and anastomose with each other in the core of the fibre. In the second place, there are no Z -lines, but in the planes where Z -lines would be expected, discrete dense-bodies are present. Similar dense-bodies occur in many smooth muscles, for example, in the mammalian uterus (Mark 1956; Shoenberg 1958), and in the anterior byssus retractor of Mytilus (Hanson & Lowy 1959 a ). The contractile apparatus of the latter closely resembles that of the oyster muscle in many respects, but the filaments are not clearly grouped into separate arrays. This feature, the presence or absence of segregated arrays of filaments, could serve as the main criterion for distinguishing striated from smooth muscles. Where the arrays of thick and thin filaments overlap in the A -bands, the two kinds of filaments appear to be cross-linked by means of transverse projections which belong to the thick filaments. The view is put forward that the paramyosin filaments are comparable to the myosin-containing filaments of the cross-striated muscles of vertebrates, and that the cross-links in the oyster muscle are comparable to actin-myosin links. The role which paramyosin filaments play in the mechanism by which certain muscles of molluscs maintain tension very economically is also discussed. The results described in this paper support the hypothesis (Lowy & Millman 1959 b , 1960) that tension is held by cross-links in a sliding filament contractile mechanism and that the economy of the system is due to a low rate of detachment of these cross-links. The alternative ‘catch’-mechanism hypothesis (Johnson, Kahn & Szent-Györgyi 1959; Johnson & Szent-Györgyi 1959; Rüegg 1959) which supposes that tension is maintained by some change of state of the protein within a paramyosin system, is difficult to reconcile with the present findings. Structures which resemble the ‘dyads’ of the cross-striated muscles of vertebrates have been found beneath the cell membrane. Their possible function in the intracellular trans­mission of stimuli is discussed in view of the fact that the fibres of the oyster muscle are only about 2 μ thick.

An Investigation of Mechanical Strength of Yarn or Cord Twisted with Other Kinds of Filaments

The object of this study is to discover the most effective law of blending and the maximum limitation on the mechanical strength of a blended yarn or cord composed of two kinds of continuous filaments. In the case of tensile rupture, the fibers making up a blended yarn resist the rupture most effectively if the mixing rate of the fibers of low extensibility is under 25% and the twist on the blended yarns is more than half the permissible maximum twist. In the case of flexing fatigue, an ideal blended cord is obtainable if the parameter of S-N diagrams and the mechanical model of the constituent fibers of the blended cord satisfy equation (27). The tensile strength or fatigue life of even the most effective blended yarn or cord is less than that of the mathematical mean of the constituent fibers. The amount of work (the degree of toughness) needed for the tensile rupture of the yarn or cord exceeds the mathematical mean of the constituent fibers.

Evidence for a Sliding Filament Contractile Mechanism in Tonic Smooth Muscles of Lamellibranch Molluscs

STRUCTURAL evidence for a sliding filament contractile mechanism in cross-striated muscles is well established1 and is based on the following points: (1) the existence of two kinds of filaments; (2) the existence of bridges between them; (3) the discontinuity of the filaments along the fibril; (4) the constancy of filament-length at different muscle-lengths; (5) the changes observed in the relative positions of the two kinds of filaments as the muscle shortens; (6) the similarity of X-ray diffraction patterns at different muscle lengths. Information about smooth muscles is much less complete, but (1) and (2) have already been demonstrated in the funnel retractor and mantle muscles of the cephalopod Loligo2, and in the pharynx retractor of the gastropod Helix2; and (6) has been shown for several smooth muscles of invertebrates3.

The Quality of Incandescent Lamps

The new specifications for incandecent lamps determine their quality in terms of life to burnout at a specified mean efficiency. Formerly it was measured by the life to 80 per cent. of initial value. The new tests, therefore, conform more nearly to the actual practise in the use of tungsten filament lamps, as many of these lamps are above 80 per cent at time of burnout. The data on carbon lamps in the paper are based on a life exponent originally determined by Mr. Howell, one of the authors of this paper. Curves showing the relation between life, efficiency and candle power was given by him in a paper presented before the Institute on April 10, 1888. Practically the same life-candle power relation has been found to apply to the GEM, tantalum and tungsten filament lamps. Nowadays the exponent used is that applying to the life-efficiency relation and is different for each kind of filament as they have different candle power-efficiency relations. All data are based on commercial ratings and guarantees. The quality of tungsten filament lamps has greatly improved since their commercial introduction in 1907 as is shown by the fact that the 40-watt vacuum lamp is now over eight times as good as then. There is a difference in the present relative quality of the various sizes of tungsten filament lamps. The 10-watt vacuum lamp, if operated at 10 mean lumens per watt, would live 190 hours and the 1000 watt gas-filled lamp 35,000 hours. The lives of other sizes of lamps at this efficiency is between these two extremes. There has been an enormous improvement since Edison's first commercial carbon lamp of 1880. It is estimated that if the present 40-watt tungsten filament lamp were made for the same mean efficiency as the 1880 lamp, the tungsten filament lamp should have a life of over a hundred and fifty thousand years. And this does not include the enormous improvement in the larger sizes of lamps due to Dr. Langmuir's invention of the gas-filled lamp. Owing to these enormous differences, the other term of quality measurement, indicating the mean efficiency for a given life, is therefore used to show the improvements since 1880. A table gives these data in chronological order. It is estimated that in 1880 about 50 lumen-hours of light were obtained for one cent, covering the cost of current and lamp renewals. The amount now obtainable is very much greater, due to lamp improvements, reduction in their prices and reduction in rates for current. The public has utilized these by using more light. With the present 40-watt tungsten filament lamps and with current at the present approximate general average rate of 4 1/2 cents kw-hr., 1700 lumen-hours can be had for one cent. It is impossible to show what part of this actual increase is due to lamp improvements except to indicate what would have been obtainable with one factor without the other. Thus had there been no rate reduction, 432 lumen-hours would now be had due to actual lamp improvements. Without the lamp improvements 190 lumen-hours would now be had due to the reduction in the general average rate. To indicate the gain due to Dr. Langmuir's invention of the gas-filled lamp, in which the high wattage sizes are the most efficient, 3820 lumen-hours can be had with the 1000 watt lamp at 4 1/2 cents per kw-hr. About half a billion dollars were spent in the United States in 1922 for current used for lighting. If the same amount of light were produced by the original 1880 bamboo carbon lamp, the cost would have been increased 3 1/2 billion dollars requiring about fifty billion extra tons of coal, equal to about ten per cent of the total coal production in the United States.