256 BOVINE PATHOLOGY. 



and there is marked swelling of the left side, which, if 

 percussed, is resonant like a drum, whence the name tym- 

 pany. Distension of the rumen impedes the action of 

 the diaphragm, and increases unduly its bulging into the 

 thorax. In some cases there is ejection of the contents of 

 the viscus. Almost always there are eructations of gases 

 with a special odour. The bowels do not act, and the in- 

 terference with the breathing increases in severity ; also 

 the brain becomes involved to a certain extent, the animal 

 loses sight, staggers, becomes insensible, and falls. Death 

 occurs either from rupture of the rumen, or from suffoca- 

 tion, or from absorption of noxious gases. The most 

 recent analysis of the gases generated in these cases is 

 given in the ^American Veterinary Review,' vol. i, p. 100 : 

 74*3 carbonic acid, 23'46 carburetted hydrogen, 2*2 

 nitrogen. Neither oxygen nor sulphuretted hydrogen 

 could be traced (Reiset). Guerin, however, found 80 per 

 cent, of sulphuretted hydrogen. 



The most fruitful cause of this disorder is green food of 

 various kinds ; it generally occurs from the voracity with 

 which cattle that have been kept on dry food all the 

 winter consume fresh provender. Hence it is most pre- 

 valent in the spring. It results from feeding on any kind 

 of green food, especially that collected when the dew is 

 on the grass ; sometimes from turnips, but generally only 

 when these are frosted or rotten. In cases of choking, 

 the mechanical impediment proves the cause. Hoven is 

 present in many cases of disorder of other organs. In 

 some cases of prostration gases are evacuated sponta- 

 taneously from the lining mucous membrane, but this is 

 very rare. Again, sudden change of diet, of any kind, 

 may cause this disorder, or deficient secretion of saliva 

 may produce the same effect. The latter cause acts as a 

 preventive to redeglutition, since the proper formation 

 of the returning pellet requires liquid admixture. 

 '^ Hoven'^ is of two kinds — acute and chronic. The latter 

 depends upon disorders of the digestive apparatus, such 

 as a want of tone of the rumen in particular, due to a 

 similar state of the system in general, and also the pre- 



