426 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS. 



It appears to be liiglily probable, therefore, that a gland 

 is originally a mass of nucleated cells, the progeny of one or 

 more parent cells ; that the membrane in connection with 

 the embryo gland may or may not, according to the case, send 

 a portion of the membrane, in the form of a hollow cone, into 

 the mass ; but whether this happens or not, the extremities 

 of the ducts are formed as closed vesicles, and then nucleated 

 cells are formed within them, and are the parents of the 

 epithelium cells of the perfect organ. 



Dr. Allen Thomson has ascertained that the follicles of 

 the stomach and large intestine are originally closed vesicles. 

 This would appear to show that a nucleated cell is the original 

 form of a follicle, and the source of the germinal spot which 

 plays so important a part in its future actions. 



The ducts of glands are, therefore, intercellular passages. 

 This is an important consideration, inasmuch as it ranges 

 them in the same category with the intercellular passages 

 and secreting receptacles of vegetables.* 



Since the publication of my paper on the secreting struc- 

 tures, in the Transactions of the Eoyal Society of Edinburgh 

 in 1842, I have satisfied myself that I was in error in attri- 

 buting to the cell-wall the important function of separating 

 and preparing the secretion contained in the cell -cavity. 

 The nucleus is the part which effects this. The secretion con- 

 tained in the cavity of the cell appears to be the product of 

 the solution of successive developments of the nucleus, which 

 in some instances contains in its component vesicles the 

 peculiar secretion, as in the bile-cells of certain Mollusca, and 

 in others becomes developed into the secretion itself, as in 

 seminal cells. In every instance, the nucleus is directed 

 towards the source of nutritive matter, the cell-wall is opposed 

 to the cavity into which the secretion is cast. This accords 

 with that most important observation of Dr. Martin Barry, on 

 the function of the nucleus in cellular development. 



* Henle, in his General Anatomy, has made a similar statement. 



