Royal Society of Edinburgh. 



255 



anatomist had hitherto " proved that secretion takes place within the 

 primitive nucleated cell itself, or had pointed out the intimate nature 

 of the changes which go on in a secreting organ during the per- 

 formance of its function." 



Numerous examples were now given of secretions detected in the 

 cavities of nucleated cells of various glands and secreting surfaces. 

 Among these were the ink of the Cephalopoda, and the purple of 

 Ianthina and Aplysia ; bile in an extensive series of animals ; urine 

 in the mollusk ; milk, &c. 



The wall is believed by the author to be the part of the cell en- 

 gaged in the process of secretion. The cavity contains the secreted 

 substance, and the nucleus is the reproductive organ of the cell. A 

 primitive cell engaged in secretion is denominated by the author a 

 primary secreting cell, and each cell of this kind is endowed with its 

 own peculiar property, according to the organ in which it is situ- 

 ated. The discovery of the secreting agency of the primitive cell 

 does not remove the principal mystery in which the function has 

 always been involved ; but the general fact, that the primitive cell is 

 the ultimate secreting structure, is of great value in physiology, inas- 

 much as it connects secretion with growth as functions regulated by 

 the same laws ; and explains one of the greatest difficulties in the 

 science, viz. why a secretion flows from the free surface only of a 

 secreting membrane : the secretion exists only on the free surface, en- 

 closed in the ripe cells which constitute that surface. 



The author then proceeded to the consideration of the origin, the 

 development, and the disappearance of the primary secreting cell ; a 

 subject which necessarily involved the description of the various 

 minute arrangements of glands and other secreting organs. After 

 describing the changes which occur in the testicle of Squalus cornu- 

 bicus, when the organ is in a state of functional activity, and in the 

 liver of Carcinus Manas, it was stated that these were selected as 

 examples of two orders of glands denominated by the author vesicu- 

 lar and follicular. 



The changes which occur in the first order of glands consist in 

 the formation and disappearance of closed vesicles or acini. Each 

 acinus might be first a single cell, denominated by the author the 

 primary or germinal cell ; or secondly, of two or more cells enclosed 

 in the primary cell, and produced from its nucleus. The enclosed 

 cells he denominates the secondary cells of the acinus ; and in the 

 cavities of these, between their nuclei and cell walls, the peculiar 

 secretion of the gland is contained. The primary cell, with its in- 

 cluded group of cells, each full of secretion, is appended to the ex- 

 tremity or side of one of the terminal ducts, and consequently does 

 not communicate with that duct, a diaphragm formed by a portion 

 of the primary cell wall stretching across the pedicle. When the 

 secretion in the group of included cells is fully elaborated, the dia- 

 phragm dissolves or gives way, the cells burst, and the secretion 

 flows along the ducts ; the acinus disappearing, and making room 

 for a neighbouring acinus which has in the meantime been advan- 

 cing in a similar manner. The whole parenchyma of glands of this 



