SPECIAL ANATOMY. 37 



2. Vascular glands. These are the Thyroid and Thymus 

 glands, Spleen and Caps, supra renales. They are soft, round, 

 or lobulated, pale or dark red, without excretory ducts. In the 

 thyroid and thymus glands small cavities are found filled with a 

 milky fluid. The parenchyma consists, in all, of granules which 

 fill up the spaces between the vessels. They are, proportionably, 

 not superabundantly, provided with blood and lymph vessels. 

 In the spleen and supra renal capsules the vessels quickly pass 

 into capillary ramifications, without marked anastomoses. In 

 the supra renal capsules a greater abundance of nerves prevails. 

 It is pretended that their function consists in producing a change 

 in the composition of the blood ; of what kind is unknown. 



With these may be classed the Lymphatic glands, which 

 consist of a convoluted arrangement of Lymphatic vessels passing 

 uninterruptedly through them (vasa offer entia and efferentia]. 

 The alteration effected in the blood and lymph as they pass through 

 them is even still doubtful. 



SPECIAL ANATOMY. 



38. General cutaneous covering of the body. 



The external surface of the body is invested by a compound 

 membrane, which, at the openings of the internal surface, turns 

 inwards, and lines the open cavities, as mucous membrane. 



39. I. External skin, cutis. 



It invests the whole of the outer surface of the body, is itself 

 covered externally with the epidermis (see Epithelium), internally 

 with loose uniting tissue, and consists of a very filamentous, 

 interwoven uniting tissue, with glands, nerves, and vessels : this 

 is the Corium. 



1. Epidermis, cuticle, is a connected, nowhere perforated, more or less 

 strong layer of pavement epithelium. Its usual thickness measures one- 

 twentieth of a line, but in the palm of the hand and under the sole of the 

 foot equals ^ to 1 line. In life colourless and diaphanous, it becomes in death 

 white arid transparent : is little elastic, but brittle, curling up together when 

 detached from the cutis, peels off, especially in cutaneous eruptions, and rises 

 in blisters on the application of heat. It does not decompose ; it is coloured 

 by sulphuric acid, brown, by nitric, yellow, by hyd. chloric, not at all, by ni- 

 trate of silver, first milky white, then greyish blue, by hyd. chlor. of gold, pur- 

 plish red. Caustic alkalies dissolve it. Elements : keratin equal to 0'94, 

 gelatin equal to 0-5, lactic acid, sulphate, phosphate of potash and lime. 



