CHAP. XXXII.] 



GLAND-CELL. 



455 





In the accompanying drawing of one of the csecal tubes of the liver of 

 the cray-fish (astacus afnnis), after 

 Leidy the gradual transition from 

 the granular matter at the bottom 

 of the follicle to the perfectly form- 

 ed cells which are being discharged 

 from its summit is well seen. 



In the glandules of Peyer, al- 

 ready described (ante p. 233), it 

 would seem that vesicles form 

 underneath, but in immediate 

 contiguity with the mucous mem- 

 brane, and becoming filled with 

 glandular contents, having the 

 nature of nuclei, exhibit a great 

 proneness to burst, and liberate 

 their contents, perhaps periodi- 

 cally, on the free surface of the 

 membrane. The ova, too, are very 

 generally elaborated in the first 

 instance in a matrix, or stroma, 

 placed beneath, and not upon, the 

 surface from which they are to 

 be discharged. But, notwithstand- 

 ing these differences, which will 

 be further considered, it must be 

 borne in mind that the gland- 

 cells, or secreting elements, in the 

 true glands, are always so placed 

 as to be able to discharge them- 



, ,- . j ,-, a. Csecal biliary tube of Cray-fish. At/, e,d,c, b, 



Selves Or tlieir prOClUCtS On the are shown cells in different stages as they advance 



c from the lower part towards the outlet. After 



outer surface. 



Of the Gland- Cell. The gland-cells select and separate from the 

 blood the substances whieh form their secreted product. These 

 elements form, in fact, in a certain sense a part of the food or 

 pabulum of these secreting cells, which is set free when the cell 

 has arrived at maturity, either by its rupture or by its complete 

 detachment from the surface upon which it has grown, or, as occurs 

 in other instances merely by transudation through its walls upon 

 one side, while new matter is supplied to it from the plasma upon 

 the other. Thus the function of secretion bears a certain analogy 

 to nutrition. The cells in both processes select from the blood 



