Ancillary Structures Research Articles

Pupillary phenomena and mechanical changes in the iris of the living rabbit

A method is described for producing and measuring distortions of the pupil in the rabbit in vivo, using magnetic forces of the order of 40–125 mg wt acting radially, for periods less than 1 sec. The radial displacement of the pupillary margin of the iris depends largely upon the size of the pupil, varying from more than 2 mm in mydriasis to less than 0·2 mm in meiosis. This is an extreme range found in twelve animals employing a force of 60 mg. When the pupil is of an intermediate size some 4–6 mm in vertical diameter a variation of the displacements may be obtained on different occasions in the same animal. This variation is probably not due to the experimental arrangement because the factor to which it is most obviously related is the direction from which the particular pupil size is reached. If a pupil of such intermediate size is reached from a position of relative meiosis such as when the light stimulus is reduced, the distortion of the pupil obtained is always definitely greater than when the pupil of that size is reached from relative mydriasis. The significance of this finding is discussed and it is suggested that the mechanical state of the iris in the rabbit is related not merely to the size of the pupil but is also determined partly by the viscoelastic properties of the ancillary structures, stroma and blood vessels as well as by the contractile elements.

The tylotrich (hair) follicle of the American opossum.

AbstractTylotrich follicles are present in the skin of the marsupial, the American opossum (Didelphis virginiana). Their morphology, ancillary structures, time of development, size and distribution of epidermal pads, are similar to tylotrich follicles found in eutherian mammals. The presence of tylotrich follicles in the marsupial suggests that they arose early in the evolution of mammalian skin.

A Dark-Age Settlements at Maxey, Northants

SUMMARYA dark-age settlement was discovered at Maxey during gravel-quarrying and partly excavated before destruction to reveal at least seven rectangular buildings ranging from 30 ft. to 50 ft. in length and 16 ft. to 20 ft. in width. They were all of post-hole construction but there were instances of post-holes in trenches, post-holes joined by wall-trenches, and, once, a central beam-slot. Near by were smaller ancillary structures including pits surrounded by post-holes, perhaps storage-huts. Open hearths, pits of various types and boundary-ditches were also found. The pottery was of an unusual type, but the small finds suggest that both it and the settlement are of the middle Saxon period.

The biochemistry of genetic factors.

The term genetic chemistry will be used in this chapter to refer to knowledge of the structure, function, replication, mode of expression, and modification of the genetic elements. The genetic elements are presently conceived to include double-stranded DNA as the genetic substance of the great majority of living organisms, single-stranded DNA as the genetic substance of certain bacterial viruses, and single-stranded RNA as the genetic substance of certain plant and animal viruses. Of necessity, discussion of the structure. replication, and expression (through the transfer of information) of these substances involves consideration of related ancillary structures, such as chromosomes and viral components. In addition to direct approaches, studies of the products of genetic action can be used as a basis for inference concerning the organization of the genetic substance, particularly when obtained under defined genetic circumstances.