THE TESTIS SPERMATIC FLUID. 551 



ter ; in that of the Dog as much as 8-72 has heen found, and in that of the 

 Sheep between 4 and 5 per cent. In the pancreatic fluid of the Horse, on the 

 other hand, the quantity of solid matter seems to be less than in the saliva. 

 Of the residuum obtained by evaporation, half appears to consist of albumen ; 

 there is also a small amount of osmazome, and apparently of casein. A free 

 acid, probably the acetic, exists in this fluid ; the salts which it contains are 

 nearly the same as those of the saliva. 



VI. Lachrymal Gland. 



698. The Lachrymal glands and their secretion may be next mentioned ; 

 but neither require any lengthened description. The gland in Man is formed 

 very much on the plan of the Parotid, being composed of branched canals ter- 

 minating in follicles, the ultimate ramifications of the several branches forming 

 lobules or divisions of the glands. The lachrymal fluid has not recently un- 

 dergone any accurate analysis ; and all that can be stated respecting it is the 

 general fact, that the quantity of solid matter in it is extremely small, and that 

 this consists chiefly of saline, and either mucous or albuminous compounds. 

 It seems probable that the secretion of the lachrymal gland itself is very little 

 else than the serum of the blood, deprived of a great part of its albumen ; and 

 that the mucus of the tears is secreted from the surface of the conjunctival 

 membrane. This secretion has a slightly alkaline re-action. It is being con- 

 stantly formed in moderate amount, for the purpose of cleansing the surface of 

 the eye from the impurities which would otherwise rest upon it ; and it is then 

 absorbed by the open orifices of the nasal duct, and carried into the nose, as 

 fast as it is poured out. The cause of this absorption does not seem very clear. 

 Capillary attraction is probably in part concerned ; and it has been thought 

 that the momentary partial vacuum occasioned by the inspiratory effort in all 

 the air-passages, will cause the emptying of the nasal duct below, and a con- 

 sequent in-draught above. The influence of the nervous system upon this 

 secretion has been already adverted to ( 425, 426). 



VII. The Testis.^- Spermatic Fluid. 



697. In the Testes we return to the tubular form of glandular structure, 

 which so remarkably distinguishes the Kidney from all the other glands 

 hitherto mentioned. The external forms presented by these glands throughout 

 the Animal kingdom, are extremely various ; but their composition is for the 

 most part very uniform. The object is sometimes attained by a simple but 

 much elongated canal ; sometimes by shorter branched tubes ; and in other 

 instances, again, by numerous aggregated cosca, which are often rounded into 

 cells. In regard to this, as to many other glands, it may be stated that, whilst 

 its general form in Insects is that of prolonged tubes, the required extension of 

 surface is given in the Mollusca by the multiplication of cells, so that the struc- 

 ture has a compact spongy character. It is interesting to remark that, in some 

 of the lowest Fishes, this organ consists of a mass of vesicles which have no 

 efferent duct ; and that the secretion formed within these escapes by the rup- 

 ture of the vesicles, allowing it to escape into the abdominal cavity, whence it 

 passes by openings that lead directly to the exterior. In these Fishes, the ova 

 are discharged from the ovarium in a very similar manner ; a modification of 

 which plan is followed in all the higher Vertebrata, the ovum being in them 

 also discharged, by the rupture of its containing vesicle or ovisac, into the 

 abdominal cavity, but immediately received and conveyed away by the funnel- 

 shaped internal prolongation of the external orifice, which is known as the 

 fimbriated extremity of the Fallopian tube.* 



* See Principles of General and Comparative Physiology, 641. 



