258 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



138. From general observations it seems conclusive that aside from 

 the presence of the virus of the disease there are certain changes in 

 the blood of advanced cases of swamp fever that are of extreme im- 



Sortance, but these are of such a nature that no method has yet been 

 evised for their accurate determination. In a broad, general way 

 it may be said that the blood is the real seat of the trouble, and that 

 any pathological changes observed in the circulatory system or in the 

 visceral organs are dependent on this rather than that the lesions in 

 the circulatory system and viscera are primary. The atrophy and 

 weakening of the muscles of the hind quarters, causing the consequent 

 staggering gait, undoubtedly are the result of metabolic disturbances 

 which are inherent in the blood rather than in the muscles themselves. 

 For the present it seems probable that as the disease progresses the 

 animal, in spite of abundant food, a vigorous appetite, and the absence 

 of any noticeable lesions in the alimentary tract, at first loses its abil- 

 ity to lay on fat, and that from this stage it draws on its body fat. 

 This certainly points to a perverted carbohydrate metabolism, and 

 all observations point to the blood as the chief seat of the disturbance. 

 The body fat undergoes a serious atrophj^, and this change may ac- 

 count for some of the edemas which are so frequently observed. 

 An experiment with the trypanbluo treatment is still under way. 

 The conclusion has been reached from the results thus far obtained 

 that natural immunity against swamp fever does exist in some horses. 

 This immunity may be increased by repeated injections of virulent 

 serum from which contaminations have been removed or by means of 

 defibrinatcd blood. 



An experimental exposure of a healthy horse which was quartered 

 in a stall adjacent to one containing a sick horse for seven months has 

 failed to transmit the disease. The discovery of a trypanosome in 

 the blood of horses in Panama affected with a disease which was diag- 

 nosed as swamp fever has been reported, but our observations made 

 in various parts of the United States do not support the results ob- 

 tained by the writer of the report in question. In fact, the results 

 have been so radically different that the question may well be asked 

 whether both series of experiments have been made upon horses af- 

 fected with the same disease, although the symptoms and lesions 

 described in both instances resemble those of swamp fever. The 

 equine trypanosomiasis of Panama seems to occupy an intermediate 

 position between the swamp fever of the United States and mal de 

 caderas of South America and to bear a very intimate relation to, if 

 it is not identical with, the Gambian horse disease of West Africa. 



CHRONIC BACTERIAL DYSENTERY. 



A COW affected with chronic bacterial dysenter}-, or Johne's disease, 

 was shipped to the laboratory from Pennsylvania and furnished 

 material for further study of the disease. The diagnosis in this ani- 

 mal was confirmed by microscopic examination of rectal scrapings, 

 which revealed the acid-fast organism of this disease in great num- 

 bers. The cow was kept isolated in a stable in which several chick- 

 ens were exposed, in order to determine whether there exists any 

 association between this disease in cattle and avian tuberculosis, as 

 has been asserted by some investigators. It is obvious that such an 

 association of chickens with an affected animal would afford a splen- 



