62 ANATOMY. 



having an indistinct or doubtful envelope, and a pale nucleus within, 

 which is rendered more visible by dilute acetic acid. These corpus- 

 cles resemble, outwardly, the white blood-corpuscles ; but differ from 

 them in being only large nuclei, and not nucleated cells. Strong 

 acetic acid only acts slightly upon them, and does not split up the 

 nucleus into separate bodies, as is the case with the nucleus of the 

 white blood-corpuscles. They have been observed to put out little 

 buds, and so to become stellate, Avhilst they may yet be supposed to 

 be living. 



The absorbents of the small intestines, called, from their milky- 

 looking contents during digestion, the lacteals, have a similar structure 

 to the lymphatics elsewhere. They commence, however, in a peculiar 

 way, as will be mentioned hereafter in the section on Absorption. 

 The milky-looking fluid which they convey during digestion, is called 

 chyle, and is characterized by containing multitudes of fine granules, 

 which are minute fatty particles enveloped by an exceedingly thin 

 film of an albuminoid substance, and constitute what has been termed 

 by Gulliver, the "molecular basis of the chyle." Besides this, the 

 chyle, after it has passed certain lymphatic glands, contains other 

 granular particles, some nuclei, and also a few of the pale lymph-cor- 

 puscles just described. Drawn from the thoracic duct, or from the 

 absorbent trunks near it, the lymph, or mixed lymph and chyle, coagu- 

 lates like the blood, the clot of the former being transparent, and of 

 the latter, of a milky color, and very soft consistence. Sometimes 

 the lymph and chyle present a reddish tinge, owing to the accidental 

 admixture of colored blood-corpuscles. The chyle, however, is sup- 

 posed sometimes to have a proper red coloring substance formed in it : 

 both fluids may become red on exposure to air. 



The secreting membranes and glands. The secreting membranes of 

 the body, already generally described, are the serous membranes, the 

 synovial membranes, the mucous membranes, and the skin. With 

 these two latter membranes are associated the glands. Speaking 

 generally, all these membranes consist of a layer of condensed areolar 

 and elastic tissue, which is very thin in the serous and synovial mem- 

 branes, thicker in the mucous membranes, and thickest of all in the 

 slun. On its under or attached side this layer contains numerous 

 bloodvessels, lymphatics, and nerves, all of which proceed to or from 

 the free surface of the membrane. Near this there is found, at least 

 in most situations, a thin stratum of a homogeneous structureless 

 membrane, called the limiting or basement membrane. Resting upon 

 this, or directly upon the condensed areolar layer, is invariably found 

 a superficial stratum of epithelial or epidermic tissue, the character of 

 which varies in different membranes, as will be presently described. 

 The mucous membranes and the skin are much thicker, more specially 

 organized, more vascular, and contain more nerves than the serous 

 and synovial membranes. 



The serous membranes, such as the arachnoid, pleura, pericardium, 

 and peritonaeum are transparent membranes arranged as closed sacs, 

 smooth on the surface, and slightly moistened with a fluid which has 

 been compared to the serum of the blood, but which resembles more 



