308 HANDBOOK OF PHYSIOLOGY. 



begin in the medullary part of the gland, and are continuous with the 

 lymph-path here as the afferent vessels were with the cortical portion; 

 the endothelium of one is continuous with that of the other. 



The efferent vessels leave the gland at the hilus, the more or less 

 concave inner side of the gland, and generally either at once or very 

 soon after join together to form a single vessel. 



Blood-vessels which enter and leave the gland at the hilus are freely 

 distributed to the trabecular tissue and to the gland-pulp. 



The Lymph and Chyle. 



Lymph is, under ordinary circumstances, a clear, transparent, and 

 yellowish fluid. It is devoid of smell, is slightly alkaline, and has a 

 saline taste. As seen with the microscope in the small transparent ves- 

 sels of the tail of the tadpole, it usually contains no corpuscles or par- 

 ticles of any kind; and it is only in the larger trunks that any corpuscles 

 are to be found. These corpuscles are similar to colorless blood-cor- 

 puscles. The fluid in which the corpuscles float is albuminous, and con- 

 tains no fatty particles; but is liable to variations according to the 

 general state of the blood, and to that of the organ from which the 

 lymph is derived. As it advances towards the thoracic duct, after pass- 

 ing through the lymphatic glands, it becomes spontaneously coagulable 

 and the number of corpuscles is much increased. 



Chyle, found in the lacteals after a meal, is an opaque, whitish, 

 milky fluid, neutral or slightly alkaline in reaction. Its whiteness and 

 opacity are due to the presence of innumerable particles of oily or fatty 

 matter, of exceedingly minute though nearly uniform size, measuring 

 on the average about -3-0^015- ^ an i ncn - These constitute what is termed 

 the molecular base of chyle. Their number, and consequently the 

 opacity of the chyle, are dependent upon the quantity of fatter matter 

 contained in the food. The fatty nature of the molecules is made mani- 

 fest by their solubility in ether. Each molecule probably consists of a 

 droplet of oil coated over with albumen, in the manner in which minute 

 drops of oil always become covered in an albuminous solution. This is 

 proved when water or dilute acetic acid is added to chyle, many of the 

 molecules are lost sight of, and oil-drops appear in their place, as the 

 investments of the molecules have been dissolved, and their oily contents 

 have run together. 



Except these molecules, the chyle taken from the villi or from lac- 

 teals near them, contains no other solid or organized bodies. The fluid 

 in which the molecules float is albuminous and does not spontaneously 

 coagulate. 'But as the chyle passes on towards the thoracic duct, and 

 especially whilst traversing one or more of the mesenteric glands, it is 

 elaborated. The quantity of molecules and oily particles gradually di- 

 minishes; cells, to which the name of chyle-corpuscles is given, appear in 



