300 MR GOODSIR ON THE ULTIMATE SECRETING STRUCTURE, 



does the semen collect on the inner surface only of the tubuli semeniferi, and not 

 on their exterior, in their interstices ? The elimination of the secreted fluid on one 

 side only of the secreting membrane, viz. on the interior of the canals, is one of 

 the greatest enigmas in physiology." MULLER proceeds to explain this enigma by 

 certain hypotheses ; but the difficulty disappears, the mystery is removed, when 

 we know that the secretion only exists in the interior of the ripe cells of the free 

 surface of the ducts or membrane, and is poured out or eliminated simply by the 

 bursting and solution of these superficial cells. 



In the former part of this paper I have confined my observations to the struc- 

 ture and function of the ultimate secreting element, the primary secreting cell. I 

 now proceed to state the laws which I have observed to regulate the original for- 

 mation, the development, and the disappearance of the primary organ. This 

 subject necessarily involves the description of the various minute arrangements of 

 glands and other secreting structures. As the development of a subject so rich as 

 this already has been, and still promises to be, would much exceed the limits of a 

 single communication, I restrict myself at present to the announcement of the laws 

 themselves, and to a statement of a few facts in illustration. I reserve for future 

 communications, which I hope to have the honour of submitting to this Society, a 

 detailed description of the minute changes which are constantly taking place in 

 glands during the performance of their function. 



If the testicle of Squalus cornubicus (GMELIN) be examined when the animal 

 is in a state of sexual vigour, the following arrangements of structure present them- 

 selves. 



The gland consists of a number of lobes separated, and at the same time con- 

 nected by a web of filamentous tissue, in which ramify the principal bloodvessels. 



The lobes, when freed from this tunic, present on their surface a number of 

 vesicles. When the gland is dissected under water, and one of the lobes is raised 

 out of its capsule, an extremely delicate duct is observed to pass from it into the 

 substance of the capsule, to join the ducts of the other lobes. 



When a section is made through one of the lobes, it becomes evident that the 

 vesicles are situated principally on its exterior. 



If a small portion be macerated in water for a few hours, and dissected with 

 a couple of needles, there are observed attached to the delicate ducts which ramify- 

 through the lobe vesicles in all stages of development. These stages are the fol- 

 lowing : 1st, A single nucleated cell attached to the side of the duct, and pro- 

 truding, as it were, its outer membrane. 



2d, A cell containing a few young cells grouped in a mass within it ; the 

 parent cell presenting itself more prominently on the side of the duct. 



3d, A cell attached by a pedicle to the duct, the pedicle being tubular, and 

 communicating with the duct ; the cell itself being pyriform, but closed and full of 

 nucleated cells. 



