570 THE SKIN. [CH. xxxvin. 



Pus occurs in the urine as the result of suppuration in any 

 part of the urinary tract. It forms a white sediment resembling 

 that of phosphates, and, indeed, is always mixed with phosphates. 

 The pus corpuscles may, however, be seen with the microscope ; 

 their nuclei are rendered evident by treatment with i per cent, 

 acetic acid, and the pus corpuscles are seen to resemble white 

 blood corpuscles, which, in fact, they are in origin. 



Some of the proteid constituents of the pus cells and the 

 same is true for blood pass into solution in the urine, so that 

 the urine pipetted off from the surface of the deposit gives the 

 tests for albumin. 



On the addition of liquor potassae to the deposit of pus cells, a 

 ropy gelatinous mass is obtained. This is distinctive. Mucus 

 treated in the same way is dissolved. 



CHAPTER XXXVIII. 



THE SKIN. 



THE skin is composed of two parts, epidermis, or cuticle, and 

 dermis, or cutis vera. In connection with the skin we shall also 

 have to consider the nails, the hairs with their sebaceous glands, 

 and the sweat glands. 



The Epidermis is composed of a large number of layers of 

 cells ; it is a very thick stratified epithelium. The deeper layers 

 are protoplasmic, and form the rete mucosum, or Malpighian layer ; 

 the surface layers are hard and horny ; this horny layer is the 

 thickest part of the epidermis, and is specially thick on the palms 

 and soles, where it is subjected to most friction. The cells of the 

 deepest layers of the Malpighian layer are columnar in shape ; 

 the layers next to these are composed of polyhedral cells, which 

 become flatter as they approach the horny layers. Between 

 these cells are fine intercellular passages, bridged across by fine 

 protoplasmic processes, which pass from cell to cell ; the channels 

 between the cells serve for the passage of lymph. It is in the 

 cells of the Malpighian layer that pigment granules are deposited 

 in the coloured races. 



Between the horny layer and the Malpighian layer are two 

 intermediate strata, in which the transformation of protoplasm 



