GLANDS. 123 



without inwardly, is composed : 1st. of a fibrous coat ; 

 2d. of a muscular coat, with both longitudinal and 

 circular fibres ; 3d. of a mucous coat, lined by simple 

 pavement epithelium. The vesiculce seminales, with 

 the exception that their walls are thinner, possess the 

 same structure as the vas deferens. 



The arteries of the testes, ramifying in the inter- ^ 8aiMi 

 lobular septa, terminate in a capillary plexus which 

 surrounds the tubuli seininiferi. The veins follow 

 the course of the* arteries. The lymphatics are very 

 numerous ; they accompany the vessels of the cord, 

 and run into the lumbar glands. The nerves, few in 

 number, follow its arteries into the parenchyma of the 

 gland, but how they terminate there is not known. 



The -semen is an alkaline liquid, destitute of color, seminal fluid. 

 in which certain accessory elements are encountered, 

 such as cells and the debris of cells, and also certain 

 essential and characteristic elements the filiform cor- 

 puscles endowed with the power of motion, and 

 known under the name of spermatozoa. These 

 curious corpuscles consist of exceedingly delicate fila- 

 ments with an almond-shaped enlargement at one 

 extremity, constituting its head, whilst the remainder 

 of the filament, tapering off to an extremely fine 

 point, represents the tail. A delicate linear depres- 

 sion, or species of collar, marks the line of junction 

 of these two portions, on the borders of which a 

 minute tubercular projection is sometimes to be seen 

 (PL XXI. fig. IV.). No trace of organization can 

 be detected, on the closest examination, in any part 

 of the spermatozoa ; the substance of which it is 

 composed being homogeneous, transparent, and amor- 



