ON THE INFECTIVE GENITAL TUMOURS OF DOGS 127 



' For the first few days after inoculation a swelling can be felt, 

 partly due to the fragments of the tumour introduced, and partly to 

 inflammatory exudation. In some cases this swelling completely 

 subsides, so that nothing can be felt until the appearance of a small 

 nodule indicates that inoculation has been successful. -In-other 

 cases the swelling persists, and it is difficult to decide whether the 

 inoculation has been successful until a definite increase in the size 

 of the swelling has taken place. The usual time at which there is 

 distinct evidence of the first appearance of the growth after inocula- 

 tion is about three weeks, but it varies between twelve days and a 

 month. . . . The small firm nodules which first appear gradually 

 increase in size, and form rounded lobulated masses. At the com- 

 mencement they are freely movable beneath the skin, but at a later 

 period the latter become thinned out, of a bluish-red colour, and 

 firmly adherent to the growths. . . . The maximum growth is 

 attained in about three months. A curious regularity obtains in 

 this respect. . . . Having reached this stage, retrograde stages are 

 not long in appearing ; the growth becomes soft and flabby, and 

 slowly dwindles until nothing is left to indicate its former presence. 

 ... In nearly half the cases the subsidence of the tumour was 

 accompanied by ulceration ; the thinned-out reddened skin giving 

 way over the growth, which has previously undergone softening, and 

 there results a deep ulcer, from which a thin grumous discharge 

 flows. Even when these retrograde changes are occurring, fresh 

 growths occasionally take place at the periphery of the tumour.' 



The histology of the tumours 1 must be carefully examined in 

 relation to the mode of evolution of the lesions as quoted above. 

 We must examine first the young tissue at the edge of a growing 

 lesion (Fig. 50), then the more advanced sarcoma-like tissue 



1 This description is based on two sections given to me by the late Dr. Wash- 

 bourn, and others kindly lent me by Mr. A. G. R. Foulerton. Dr. Washbourn's 

 had been fixed in some osmic acid medium and stained with haematoxylin. The 

 osmic acid had prevented a good colour differentiation, a fact that explains the 

 unsatisfactory character of the illustration that appears in his original paper. After 

 bleaching one of the sections in io-volume solution of peroxide of hydrogen and 

 restaining with acid hasmatoxylin and eosin, I obtained a very fair differentiation. 



