142 SKIN. 



and external aspect of the thigh. The bloodvessels can be 

 best studied in injected preparations, for which purpose the 

 best way is to inject one of the upper extremities of a new- 

 born foetus. 



The lymph vessels can be made out most easily in cedema- 

 tous skin. The integument must be removed with the whole 

 of the subcutaneous tissue, and then sacrificed at one or two 

 points, and left twenty- four hours suspended, until much of 

 the liquid has drained away. The vessels can then be injected 

 by the puncture-method. 



The preparation of the nerves and cellular elements of the 

 corium and papillae by the gold method has been already cle- 

 cribed. The Pacinian corpuscles and tactile corpuscles of 

 Meissner can be advantageously seen in thin sections of the 

 volar side of the finger or palm, after hardening in chromic 

 acid. 



Sweat Glands. The sweat glands are of two forms. 

 Those of the first form are long and slender tubes closed at 

 one end. The secreting part, or body of the gland, is convo- 

 luted, and is imbedded in the subcutaneous tissue at a variable 

 depth ; the duct which passes through the corium to the sur- 

 face follows a slightly winding course. The gland, whether 

 seen in transverse or longitudinal sections, is found to be 

 limited by a fine membrane (membrana propria) lined by a 

 single layer of cylindrical epithelium, the free surface of which 

 forms the internal surface of the gland. In very thin sections, 

 in which it is possible to compare the epithelium of the ducts 

 with that of the body of the gland, it is seen that the elements 

 of the former are more slender. In the duct it is further note- 

 worthy that the nucleus of each element is in its outer third, 

 and that the nuclei are regularly arranged. In the elements 

 of the body of the gland they lie in the middle of each cell. 

 In the epidermis, the duct is continued towards the surface as 

 a canal, which winds spirally, like a corkscrew. This is par- 

 ticularly the case when the epidermis is of some thickness. 



In a section which shows the whole course of the canal, it 

 is seen that the membrana propria becomes continuous with 

 the most superficial layer of the corium, while the epithelium 

 of the duct becomes identified with the elements of the rete 

 Malpighii. This first form of sweat glands is met with over 

 the whole integument. The glands of the second form occur 

 along with the others in grown persons only, and are subject 

 to great differences as regard their distribution. They are 

 always to be found in the skin of the palm of the hand, of the 

 axilla, and of the scalp. They are met with in some persons 

 in other parts of the body. They are distinguished from the . 

 common form by the facts that they are three or four times 

 as large, that the tube is as much wider, and that the epithelium 



