Supplement to the Observations on the Innervation of Lung in Dog

Abstract

In the large and intermediate bronchial branches of the lungs of dog, cartilages of various sizes are found circularly arranged in 3-4 rows. The smooth muscle layer under the propria is well developed, but the bronchial glands showing serous nature are very poor in development.In the small bronchial branches the cartilages are arranged generally piecewise in one row and the muscle layer is well developed, but here too the bronchial glands are in poor development. In the bronchioli also the muscle tissue is very good in development, so that the propria is nearly all taken up by the muscle layer. In the bronchioli respiratorii the epithelium is of the single-rowed cylinder and cubic type and is lined on the outside by a circular muscle layer still in good development. In the alveolar ducts also pieces of muscle tissue are seen here and there.Perichondral and subchondral plexuses are demonstrated to exist in the intrapulmonary bronchial wall. The former is found as loose-knit networks around the outermost cartilages and contain ganglia, large and small. The latter is very small-scaled plexus formed on the inside of the innermost cartilages by fine bundles originating in the perichondral plexus. In the smaller bronchial branches lacking cartilages the distinction of the two kinds of plexus is naturally obliterated, only plexus of small bundles being observed outside the muscle layer. These tiny plexuses also contain some small ganglia.The ganglion cells may be classified into two types-Type I and Type II-but I found mixed form of the two types not rarely. In my sections of the canine lungs, the cells of Type I somewhat exceeded those of Type II in number.The ganglion cells may be divided into the large, the intermediate and the small types. Their nuclei are usually round and in Type I cells, are mostly located eccentrically or even marginally. As SATO has observed in his study, I also found that the size of the nuclei increased in a slow arithmetic progression as the diameter of the cells increased more rapidly.Among the cells Type I, the cells with a central standing nucleus are round in form and their nerve processes run out of the cell body all-sidedly. When the nucleus is eccentrically or polarly standing, the nerve processes emerge from the cell surface opposite to the nucleus pole. The plasmodium around the cell is strongly developed, containing many special nuclei, near this process pole.Among the Type I cells, some cells with short processes returning to the mother cells forming windows (fenestrated cells) and with processes ending in end-lamellae were found, but none with processes terminating in rings.The cells with polarly standing nuclei in dog lung can be divided into octopus type cells and jelly-fish type cells, according to the course forms of their short processes, but in size they are inferior to those observed by SATO in human sympathetic trunk ganglia. Spiral type cells were hardly encountered.The Type II cells are mostly round and the nerve processes run out of the cell surface indifferently from all sides. Their short processes end in sharp points extracapsularly, often after undergoing ramification. Not rarely, however, do they terminate in end-knobs, and anastomosis between short processes from two neighbouring Type II cells is also frequently observed.The termination of the external vegetative fibres running into the ganglia is represented by the terminal reticulum commonly surrounding the ganglion cells, which partially runs into the accessory cell plasmodium but does not come into direct connection with the nerve cell.In the lungs of dog also the vegetative fibres end in the terminal reticulum. This terminal reticulum is especially well developed in the arteries and in the muscle layer. It comes only in contact with the surface of the cells but does not penetrate into their protoplasm nor sends branch elements into them.