1879.] 



Serous Glands in Rest and Activity. 



381 



were the following : — In some adult rabbits in digestion the clear zone 

 was very doubtfully apparent; in some young rabbits in hunger there 

 were distinctly two zones, and in one or two of adult and young 

 sympathetic stimulation produced but very little effect. 



Nussbaam # found that the transition cells stained black with osmic 

 acid, whilst the alveolar cells were but lightly coloured. His con- 

 clusion from this that the transition cells formed the ferment was 

 contested by me f on the ground that if the gland were treated with 

 alcohol before treating with osmic acid, the transition cells did not 

 stain black, and that it was highly improbable that the ferment had 

 been dissolved by alcohol. Nussbaum, in a later paper, J upholds his 

 opinion and rejects my argument on the ground that he can obtain a 

 substance from the gland which is insoluble in alcohol, and which yet 

 does stain black with osmic acid, this substance being the ferment. 



It is a matter easy to decide ; a fresh gland is placed in absolute 

 alcohol for twenty-four hours ; sections are made and placed in 

 osmic acid one per cent, for the time mentioned by JSTussbaum, 

 viz., two hours, and examined. The whole has a yellowish-brown 

 tint, the transition cells are but a trifle more deeply stained than 

 the alveolar cells; they have to be looked for instead of striking 

 the eye in the manner they do when the gland is treated with osmic 

 acid first and alcohol afterwards. A stay of twenty-fours in the acid 

 does not materially alter the appearances. It is, perhaps, hardly 

 necessary to bring forward my original argument ; for numerous 

 later experiments have shown me that the prominence of the transition 

 cells and their depth of tint depend on the subsequent treatment 

 with alcohol rather than on the prior treatment with osmic acid. The 

 gland, placed in osmic acid one per cent, and that only, for two 

 hours, has the ducts darkest stained, the transition cells are 

 slightly deeper in tint than the alveolar cells, mainly because the former 

 are evenly stained throughout, whereas the latter are not ; both are 

 yellowish-brown. One, two, or even more days do not make the 

 transition cells conspicuous. But if, after two hours in osmic acid, the 

 glands are placed in dilute alcohol 50 to 75 per cent, for twenty- 

 four hours, sections show the brown-black clumps of the transition 

 cells scattered amongst the much lighter-coloured alveoli. The ducts 

 are in this case equally or even less dark than the transition cells- 

 If alcohol be used absolute instead of diluted, the appearances are 

 similar, but in the first day or two at any rate, less marked. 



In other glands, too, I have found that the selective staining of 

 osmic acid is best brought out by subsequent treatment with alcohol. 



The resting and active glands treated with osmic acid and alcohol 



* Max SchUltze. "Arch. f. Mik. Anat.," Bd. xiii, p. 724, 1877. 



f Foster. "Journal of Physiology/' vol. i, p. 68, 1878. 



% Max Schiiltze. " Aivh. f. Mik. Anat.," Bd. xyi, p. 543, 1879. 



