422 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS. 



In the centre of the lobe, where the smaller ducts meet to 

 form the principal duct, there is a mass of grey gelatinous 

 matter through which the ducts pass. This gelatinous matter 

 consists of a number of cells lying between the converging 

 ducts, and from their peculiar appearance not presenting the 

 usual nuclei. I am inclined to believe that they are either 

 vesicles which have never become developed on account of the 

 pressure of the surrounding parts, or that they are old vesicles 

 in a state of atrophy after the expulsion of their contents. 



Having now described the changes which are constantly 

 taking place in the testicle of this shark when the organ is in 

 a state of functional activity, I must defer till a future occa- 

 sion an account of similar changes which occur in the paren- 

 chyma of an order of glands, of which the one already 

 described may be considered as a type. I may state, how- 

 ever, that I have ascertained the following general facts in 

 reference to glands of this order : 



1st, The glandular parenchyma is in a constant state of 

 change, passing through stages of development, maturity, and 

 atrophy. 



2d, The state of change is contemporaneous with, and 

 proportional to, the formation of the secretion, being rapid 

 when the latter is profuse, and vice versa. 



3d, There are not, as has hitherto been supposed, two 

 vital processes going on at the same time in the gland, growth 

 and secretion, but only one viz. growth. The only difference 

 between this kind of growth and that which occurs in other 

 organs being, that a portion of the product is, from the 

 anatomical condition of the part, thrown out of the system. 



4:th, The vital formative process which goes on in a gland 

 is regulated by the anatomical laws of other primitive cellular 

 parts. 



5th, An acinus is at first a single nucleated cell. From 

 the nucleus of this cell others are produced. From these, 



