300 EXTERNAL GENERATIVE ORGANS, BY E. KLEIN. 



same mode as in the thyroid gland. Such yellow and brown pigment 

 scales, and fusiform cells containing pigment granules, may be found 

 both in the cortex and in the gland substance. 



A peculiar organ exists in the upper and posterior segment of the 

 prostate, presenting the aspect of a large duct, the wall of which 

 resembles that of an artery, being composed of an internal longitudinal, 

 a middle circular, and an external longitudinal layer. The middle 

 layer consists chiefly of smooth muscular fibres, whilst these are less 

 numerous in the internal and external layers. The interior of this 

 structure is filled with numerous small vascular plexuses, pigmentary 

 concretions, and trabeculae of smooth muscular fibres. 



Fig. 214 B. 





Fig. 214s. Section through the central gland substance of the 

 prostate of an adult, as seen with Hartnack's objective system No. 5, 

 ocular 3. 



The prostate is always present in Mammals, but there is no analo- 

 gous organ in Birds. In the urodelous Batrachia, the pelvic and anal 

 glands, that swell up during the procreative season, and discharge 

 their secretion into the cloaca, may perhaps correspond to the prostate 

 and the glands of Cowper. Similar organs open into the cloaca of 

 Saurians. In Fishes there are aggregations of acini that communicate 

 with the vas deferens by means of ducts (Ley dig). 



V. COLLICULUS SEMINALIS. The colliculus seminalis is in- 

 vested by a beautifully laminated pavement epithelium. This 



