370 



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

 creting 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 desci-iption 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 meenas, it was stated that these were selected as 

 examples of two oi'ders of glands denominated by the author vesicu- 

 lar and follicular. 



The changes which occur in the first oi'der consist in the forma- 

 tion 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 aci- 

 nus, 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 included group of cells, each full of secretion, is appended 

 to the extremity or side of one of the terminal ducts, and consequent- 

 ly does not communicate with that duct, a diaphragm formed by a 

 portion of the primary cell- wall stretching across the pedicle. ^\Tien 

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

 diaphrao-m dissolves or gives way, the cells burst, and the secretion 

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

 a neighbouring acuius, which has in the mean time been advancing 

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

 is thus, according to these obsex'vations, in a constant state of change, 

 — of development, maturity, and atrophy, — this series of changes 

 being directly proportional to the profuseness of the secretion. 



In the second order of glands, the follicular, as exemplified in the 

 liver of Carcimts meenas, the germinal cell or spot, is situated at the 

 blind extremity of the follicle, and the secreting cells, as they ad- 

 vance along the follicle, become distended with their peculiar secre- 

 tion. 



Amonof other seneral conclusions deducible from these observa- 

 tions, it appeared that ducts are to be considered as intercellular 

 passages, into which the secretions formed by cells are cast. 



