332 SOLID PARTS OF ANIMALS. 



tunica albuginea, occupying the anterior part of the process of it 

 called mediastinum. The blood-vessels occupy the posterior 

 part These vessels constitute what is called rete testis. Being 

 less convoluted than the tubuli, they are called vasa recta. Their 

 direction is backwards and upwards to reach the posterior and 

 upper part of the testis. The vasa recta are not so numerous? 

 but larger than the tubuli seminiferi^ from which they receive the 

 secretion ; but they are more numerous and smaller than the 

 vessels into which they discharge it. 



These are the vasa efferentia. They are from twelve to fifteen 

 in number, and open separately into a single vessel of which the 

 epididymis is formed. This vessel or tube is very much convo- 

 luted, and the convolutions are united together by small fibrous 

 bands. It terminates in the vas deferens, which is the excretory 

 duct of the testis. 



From the preceding description, it is evident that the testis is 

 composed almost entirely of tubes and blood-vessels connected 

 together by fibrous bands. It would be next to impossible to se- 

 parate the different vessels from each other, so as to be able to 

 examine each kind separately. And from the great minuteness 

 and thinness of the tubes, the different coats of which they are 

 composed cannot be recognized, far less separated from each 

 other. We need not be surprized, therefore, that no attempt 

 has hitherto been made to determine the chemical constitution 

 of the testes. 



3. The lachrymal gland is placed at the upper and outer part 

 of the orbit, near its anterior border, corresponding with the la- 

 chrymal fossa in the orbital plate of the frontal bone. The 

 gland is convex on its upper surface. Its under surface is con- 

 cave, where it rests on the globe of the eye, the recti muscles 

 interposing. Its length is three-quarters of an inch, its breadth 

 half-an inch. It is divisible into two lobes, so closely connected 

 that the line of separation is not easily seen. When stript of the 

 cellular tissue it is observed to be composed of a number of gra- 

 nules, each forming a secreting structure, which produces the 

 tears. From the granules arise excretory ducts, which emerge 

 from the gland at its anterior border, run downwards and in- 

 wards close to the conjunctiva, and open in a row upon its free 

 surface about three lines above the upper margin of the tarsal 

 cartilage. These ducts are usually seven in number. 



