THE LYMPHOGENIC DIATHESIS. 449 



continue in use. At the present moment it is difficult to determine 

 the question. Under any circumstances it has the advantage of 

 inchiding diseases of the lymphatic system, indicated by hypertrophy 

 of the lymphatic glands (adenitis) . or by an exaggerated production of 

 white l)lood corpuscles (leucaemia), and the passage into the general 

 circulation of products derived from the lymphatic apparatus. For 

 these reasons it may be employed here. 



Clinical investigation long ago demonstrated that in man certain 

 pathological conditions were characterised by a peculiar colour of the 

 blood, due to the presence of white blood corpuscles in excessive 

 quantities, whence the names " leucaemia " (Virchow) and " leuco- 

 cythaemia " (Bennett). In the same way it has been shown that the 

 change in the blood characterised by a superabundance of white blood 

 corpuscles generally coincides with engorgement or more or less 

 marked hypertrophy of the lymphatic system and of the adenoid 

 tissue of the body (lymphatic glands, spleen, bone marrow, and, in 

 exceptional cases, liver, kidneys, etc.) — leuco-cythaemic lymphadenitis ; 

 but that many cases also occur in which this hypertrophy of the 

 adenoid tissue or of the lymphatic gland tissue may exist, without 

 any excessive number of white blood corpuscles in the blood, whence 

 the name " aleucaemic lymphadenitis or pseudo-leucaemia." Cases of 

 true leucaemia without adenitis are much rarer, the lesions therein 

 being confined to the adenoid tissue of the bone marrow. 



These three morbid conditions — leucaemic lymphadenitis, or leuco- 

 cythaemia ; aleucaemic or pseudo-leucaemic lymphadenitis, or more 

 simply adenitis ; and true or simple leucaemia — are frequently found 

 in the bovine species. Whilst stating that these diseases are frequent, 

 we must, however, be understood to excej^t the numerous cases of 

 tuberculous lesions formerly included under the same head. 



Jaccoud has shown that in reality the causes of these three morbid 

 conditions are very similar, and that a case which at first appears to 

 be of the nature of aleucaemic lymphadenitis may later become trans- 

 formed into leucaemic lymphadenitis; or, inversely, that a case which 

 at first appeared to be a simple leucaemia might often become com- 

 plicated with lymphadenitis : hence the grouping of these different 

 morbid conditions under the heading of lymphogenic diathesis. 



Investigations have now thrown more light on the subject because of 

 the more perfect recognition of the varieties of white blood corpuscles, 

 and the above-mentioned morbid conditions may be defined as follows : — 



(1.) The first variety consists of a more or less marked adenitis or 

 lymphadenitis without leucaemia (aleucaemic lymphadenitis). 



(2.) The second variety, consisting of leucaemic lymphadenitis, or 

 leuco-cythaemia, is a lymphatic lucaemia or lympho-cythaemia, the 

 D.c. G G 



