QUARTERLY CHRONICLE OF MICROSCOPICAL SCIENCE. 185 



only exists — those, namely, distinguished hy Heidenhain as 

 " investing cells." The same was true of the tortoise ; but 

 in this animal the pyloric glands differ much from those of 

 the rest of the gastric nnicous membrane, containing, up to 

 the very end, cylindrical cells, while the others are filled Avith 

 " investing cells." The stomach of a snake {^Coronclla 

 Icsvis) showed also investing cells at the closed ends of the 

 follicles ; but in the neck of the gland large vesicular cells, 

 like those described by Heidenhain in the peptic glands of 

 the frog, and regarded by him as mucus-cells. In order to 

 test the hypothesis of Heidenhain, that the investing cells 

 secrete acid only, while his "capital or chief cells" produce 

 pepsin, Friedinger made certain experiments on digestion, 

 the general result of which was to contradict Heidenhain's 

 hypothesis, as well as the confirmatory experiments of Eb- 

 stein, who had sought to prove that the pyloric glands, which 

 contain, according to him, cells analogous to the investing 

 cells of the gastric glands, also produced pepsin. 



Friedinger, repeating the same experiments more carefully, 

 found the pyloric glands to possess little or no digestive 

 power, while he considers their cells as comparable to the 

 chief cells of the gastric glands, and, accordingly, is led to a 

 hypothesis precisely the converse of H idenhain's, namely, 

 that the cells usually described by previous authors as peptic 

 cells are really those which produce pepsin, though it is to 

 these that Heidenhain gives th2 name of investing cells, and 

 ascribes the production of acid only. 



XI. Muscle. — Merkel (Schultze's ' Archiv,' vol. viii, p. 244, 

 18T2) has published a careful memoir on striated muscle, 

 confining himself for the present to the Arthropoda. In a 

 short historical notice he mentions the new interpretation 

 given by Krause, who, seeing a line in the singly refracting 

 substance of muscle, regarded it as a transverse disk, dividing 

 the substance into two halves, so that a single muscle ele- 

 ment consists according to him of one half a mass of singly 

 refracting substance, a whole doubly refracting portion, and 

 again one half singly refracting. This whole series is 

 enclosed in a sort of box, or muscle compartment formed by 

 a membranous tube closed at each end. In Hensen's memoir, 

 published about the same time, this observer also claims to 

 have discovered a new transverse disk, only this lime not in 

 the singly but in the doubly refracting substance. He thus 

 regards the muscle element as made up successively of one 

 half doubly refracting substance, one singly refracting, and, 

 again, otte half doubly refracting. It would be easy to iden- 

 tify these views if we could suppose that one or the other 



VOL. XII. NEW SER. O 



