492 LECTURE XIX. 



exuded fluids, and gradually becoming more numerous 

 supplied the pus. But the matter is on this wise, that, 

 the longer the suppuration lasts, the more certainly is 

 one series of cells after the other in the rete involved 

 in the process of proliferation, and that, whilst the 

 vesicle is rising up, the quantity of the cells which grow 

 into its cavity is constantly becoming greater. When 

 a variolous pustule forms, there is at first only a drop 

 of clear fluid present, but nothing arises in it ; it only 

 loosens the neighbouring parts of the rete Malpighii. 



Precisely the same is the case with mucous membranes. 

 There is not a single mucous membrane which may not 

 under certain circumstances furnish puriform elements. 

 But here too a certain difference always presents itself. 

 A mucous membrane is all the more in a condition to 

 produce pus without ulceration, the more completely the 

 epithelium it possesses is stratified. All mucous mem- 

 branes with a single layer of cylindrical epithelium (intes- 

 tines),* are much less adapted for the production of pus ; 

 that which is produced on them, even though it have 

 quite the appearance of pus, frequently turns out upon 

 close examination to be only epithelium. The intestinal 

 mucous membrane, especially that of the small intestine, 

 scarcely ever produces pus without ulceration. The 

 mucous membrane of the uterus, and of the fallopian 

 tubes, though it is frequently covered with a thick mass 

 of quite a puriform appearance, almost always secretes f 



* In the air passages (nose, larynx, trachea, bronchi) we commonly find several 

 layers of cylindrical epithelium lying one above the other. From a MS. Note by the 

 Author. 



f Secrete in this and similar places does not of course mean to separate from the 

 blood, but from the tissue itself, whose elements (cells) are separated (detached) at 

 the surface, and, when mixed with the serous effusion from the blood, removed. 

 The detachment of the cells is effected sometimes by means of the fluid which trans- 

 udes from the blood, sometimes by the continual growth of a succession of new celli 

 beneath them, and sometimes in consequence of their own round form. In desqua- 

 matiou of the cuticle the second of these methods, in sev >ral forms of catarrh the 



