302 MR GOODSIR ON THE ULTIMATE SECRETING STRUCTURE, 



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 de- 

 fer till a future occasion an account of similar changes which occur in the paren- 

 chyma of an order of glands, of which the one already described may be consi- 

 dered as a type. I may state, however, that I have ascertained the following ge- 

 neral 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, This 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. 



4th, 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, again, others arise in the same manner. 

 The parent cell, however, does not dissolve away, but remains as a covering to the 

 whole mass, and is appended to the extremity of the duct. Its cavity, therefore, 

 as a consequence of its mode of development, has no communication with the duct. 



The original parent cell now begins to dissolve away, or to burst into the 

 duct at a period when its contents have attained their full maturity. This period 

 varies in different glands, according to a law or laws impressed upon each of them. 



6th, In the gland there are a number of points from which acini are deve- 

 loped, as from so many centres. These I denominate the germinal spots of the 

 gland. 



7th, The secretion of a gland is not the product of the parent cell of the 

 acinus, but of its included mass of cells. The parent cell or vesicle may be de- 

 nominated the primary cell ; its included nucleated cells, after they have be- 

 come primary secreting cells, may be denominated secondary cells of the acinus. 



8th, The matter which passes off by a duct of a gland may be, 1st, A true 

 secretion, that is, matter formed in the primary secreting cell cavities ; or, 2d, A 

 mixture of a fluid formed in these cell cavities with the developed or undeveloped 

 nuclei of the cells themselves ; and, 3d, It may be a number of secondary cells 

 passing out entire. 



If a portion of the liver of Carcinus Manas is carefully examined, it is ob- 

 served that each of the follicles of which it consists presents the following struc- 



