298 MR GOODSIR ON THE ULTIMATE SECRETING STRUCTURE, 



The generative cseca of Echiurus mdgaris (LAMARK) contain cells full of 

 minute spermatozoa. 



Aplysia punctata secretes from the edge and internal surface of its mantle a 

 quantity of purple fluid. The secreting surface of the mantle consists of an ar- 

 rangement of spherical nucleated cells, about 3.000th of an inch in diameter. 

 These cells are distended with a dark purple matter. 



The edge and internal surface of the mantle of Janthina Fragilis (LAMAKK), 

 the animal which supplied the Tyrian dye, secretes a deep bluish purple fluid. 

 The secreting surface consists of a layer of nucleated cells, about 2.000th of an 

 inch in diameter, distended, with a dark purple matter. 



If an ultimate acinus of the mammary gland of the bitch be examined during 

 lactation, it is seen to contain a mass of nucleated cells. These cells are generally 

 ovoidal, rather transparent, and measure about 2.000th of an inch in the long dia- 

 meter. Between the nucleus and the cell wall of each, a quantity of fluid is con- 

 tained, and in this fluid float one, two, three, or more oil-like globules, exactly re- 

 sembling those of the milk. 



In addition to the series of examples already given, I might adduce many 

 others to prove that secretion is a function of the nucleated cell. Some secretions, 

 indeed, are so transparent and colourless, as to render ocular proof of their origi- 

 nal formation within cells impossible ; and we do not yet possess chemical tests of 

 sufficient delicacy for the detection of such minute quantities. The examples I 

 have selected, however, shew that the most important and most striking secretions 

 are formed in this manner. The proof of the universality of the fact, in reference 

 to the glandular structures which produce colourless secretions, can only rest at 

 present on the identity of the anatomical changes which occur in their cellular ele- 

 ments. This part of the proof I shall enter upon in another part of the paper. 



The secretion within a primitive cell is always situated between the nucleus 

 and the cell-wall. Now, as we know that the nucleus is the reproductive organ of 

 the cell, that it is from it, as from a germinal spot, that new cells are formed, I am 

 inclined to believe that it has nothing to do with the formation of the secretion. I 

 believe that the cell-wall itself is the structure, by the organic action of which each 

 cell becomes distended with its peculiar secretion, at the expense of the ordinary 

 nutritive medium which surrounds it. 



The ultimate secreting structure, then, is the primitive cell, endowed with a 

 peculiar organic agency, according to the secretion it is destined to produce. I 

 shall henceforward denominate it the primary secreting cell. It consists, like 

 other primitive cells, of three parts, the nucleus, the cell-wall, and the cavity. The 

 nucleus is its generative organ, and may or may not, according to circumstances, 

 become developed into young cells. The wall is the organ by the agency of which 

 the cell performs the duty assigned to it. The cavity is the receptacle in which 



