68 



LECTURE II. 



Generally speaking, therefore, glands consist of accu- 

 mulations of cells, which usually form open canals. With 



FIG. 18. 



the exception of the glands, whose functions are uncer- 

 tain, such as the thyroid body and supra-renal capsules, 

 there are in the human body only the ovaries which form 

 an exception to this rule, inasmuch as their follicles are 

 only open at times ; yet they too must be open when 

 the specific secretion of the ova has to take place. In 

 most glands there is found indeed besides a certain quan- 

 tity of transuded fluid, but this only constitutes the 

 vehicle which floats off either the cells themselves, or 

 their specific products. Suppose, for example, that in 

 one of the ducts of the testicle a cell, in which there is 

 a production of spermatozoa, becomes detached, then there 

 transudes at the same time a certain quantity of fluid, 

 which carries them away ; but what makes the semen, 

 semen, and constitutes the specific character of the action 



Fig. 18. A. Development of sweat-glands by means of the proliferation of the 

 cells of the rete Malpighii in an inward direction, e. Epidermis, r. Rete Malpighii. 

 g g. Solid process, constituting the first rudiments of a gland. After Kolliker. 



B. Portion of the duct of the sweat-gland in a state of complete development. 

 t t. Tunica propria. e e. Layers of epithelium. 



