1 80 EMBRYOLOGY. 



leaves the Fallopian tube it has gained an albuminous coat which 

 would probably be impervious to the spermatozoa.' (3) The unim- 

 pregnated egg degenerates before it enters the uterus, and is then 

 probably incapable of impregnation. 



What are the seminal vesicles? 



They are tubules which join the vasa deferentia, and lie upon 

 the base of the bladder, emptying into the urethra by the ejacu- 

 latory ducts through the prostate gland. In structure the vesiculae 

 seminales are convoluted. They are lined by a mucous membrane 

 which is convoluted and folded so as to give it a sacculated 

 appearance. 



What is the prostate gland? 



It is a gland lying at the base of the bladder and surrounding 

 the urethra at its beginning. It has the general structure of the 

 glandular organs, and in addition a considerable amount of muscu- 

 lar tissue. Its acini empty into ducts which empty in the urethra. 

 Its function is not exactly known. 



Describe the penis. 



It consists of three more or less cylindrical bodies of erectile 

 tissue enclosed in fibrous sheaths. The two corpora cavernosa lie 

 above, and receive between them, below, the corpus spongiosum, in 

 which the urethra is contained. The glans penis is continuous 

 w r ith the corpus spongiosum. The covering of the penis is of 

 loose skin, but over the glans penis and lining the prepuce it 

 resembles mucous membrane. In this region there is an abundant 

 subcutaneous nerve-plexus, and the Pacinian bodies are quite 

 numerous, so that it is possessed of acute sensibility. 



Describe the urethra. 



It extends from the. bladder through the corpus spongiosum to 

 the end of the penis. It is lined with mucous membrane, and is 

 furnished in its deeper layers with numerous muscular fibres 

 There are a number of ducts of glands opening into it whose 

 function is not fully understood, though their secretion is sup- 

 posed to be added to that of the seminal vesicles to make up the 

 semen. 



How is the erectile tissue of the penis arranged ? 



The erectile tissue consists of a system of distensible veins lying 

 in the interstices of a fibrous connective tissue. The erector 



