152 A Manual of Veterincvry Physiology. 



either acid or alkaline, both leading to the production of 

 marsh gas ; but the acid fermentation occurs iu the 

 presence of skatol, whilst the alkaline occurs in the 

 presence of indol (Ellenberger). Intestinal fermentation in 

 the horse is allied to that occurring in the rumen of 

 cattle. In all cases the fermentation can occur without the 

 presence of oxygen. 



By the decomposition of starchy matters lactic, formic, 

 acetic, butyric, and propionic acids are formed. It is to 

 some of these that the acid reaction of normal fieces is due. 



In the large intestines of horses Colin describes no less 

 than eight or ten species of Infusoria. The most charac- 

 teristic of these are the Colopodes, recognisable by their 

 ovoid form, with lateral indentation, at the base of which 

 the mouth is found. Others have an ovoid form but lack 

 the lateral indentation of the previous species ; some have 

 an elongated rectangular form, and others are unsym- 

 metrical in shape. All these infusoria are found in the 

 caecum and anterior parts of the double colon ; they die in 

 the last part of the intestines, and leave nothing more than 

 their debris in the excreta. In ruminants similar organisms 

 are found in the rumen. As to the action of these organ- 

 isms we know nothing. 



The largest amount of gas found in the intestinal canal 

 is in the caecum and colon. The small intestines do not 

 naturally contain much, whatever is formed there being 

 probably rapidly passed into the large bowels. In these 

 intestines we know that marsh-gas commonly exists, form- 

 ing, with CO., the bulk of the gases present in these parts. 

 We are all practically aware of the conditions arising in 

 horses in the large bowels, and in cattle in the rumen, as 

 the result of the fermentation of food — particularly green 

 grass — and the enormous size to which the animal may be 

 distended. In both the gas may generally be ignited a 

 short distance away from the cannula, which has been 

 passed into the parts to give relief, the CH 4 , or marsh-gas. 

 igniting readily on meeting with the proper proportion of 

 oxygen. 



