THE LYMPHOGENIC DIATHESIS. 451 



symmetrical hypertrophy of all the lymphatic glands; the spleen is 

 very often enormous, and the liver is sometimes affected, as are also, 

 in exceptional cases, the kidneys. 



It may happen that the spleen alone appears affected, or at least 

 that it has been first attacked, a fact which explains the existence of 

 leucaemia before any enlargement of the lymphatic glands. 



Causation. The causes of lymphadenitis and of lympho-cythaemia 

 are unknown in veterinary as in human medicine. Apparently these 

 diseases are more common in adults than ia young animals. Some 

 regard them as infectious in character, but this can hardly be the 

 case, as all experimental attempts to transmit the diseases have failed. 

 It is more plausible to compare the development of these morbid 

 conditions with that of malignant tumours, and although some doubt 

 still exists, simple lymphadenitis may be described as an aleucaemic 

 lymphoma or lympho-cytoma, which has gradually become generalised, 

 spreading by way of the lymphatic channels from the gland first affected 

 through the surrounding glandular system. Lympho-cythaemia, on the 

 other hand, may be said to be a leucaemic lympho-cytoma, which spreads 

 both by the blood circulation and by the lymphatic paths (spleen, 

 haematopoietic glands and organs). 



This view of the development of the lesions enables us to class 

 lympho-sarcomata with lymphomata and lympho-cytomata. The 

 malignant character and extremely rapid development of lympho- 

 sarcomata appear due to its extending by contiguity of tissue, and 

 simultaneously by the lymphatic paths. 



This new grouping would consequently place on one side myelof^enic 

 leucaemia, also called myelo-cythaemia, which is perhaps a different mor- 

 bid species. This would destroy the unity implied in Jaccoud's theory 

 of the lymphogenic diathesis ; but for all that this method of grouping 

 might be justified by reference to specific cellular characteristics. In 

 myelo-cythaemia the disease appears to commence as a lympho- 

 cythaemia, i.e., it is unaccompanied by enlargement of lymphatic 

 glands or hypertrophy of the spleen or liver, though the blood ap- 

 pears leucaemic. The condition is not a leucaemia due to lympho- 

 cytes, but rather a leucaemia produced by mono- and poly- nuclear 

 eosinophile leucocytes, i.e., leucocytes derived from the bone marrow. 



The patients are carried off rapidly after persistent wasting, decline 

 and cachexia, whilst on post-mortem examination the puriform aspect 

 of the bone marrow is an extremely striking characteristic. 



Diagnosis. There is rarely much difldculty as regards the diagnosis. 

 The enlargement of the lymphatic glands, for instance, can readily be 

 detected, and the only disease with which this can possibly be confounded 

 is tubercular enlargement. 



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