12 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. 



right sac differs in having a soft membrane with an epithelium 

 formed by a single layer of cells. 



G. intestinalis larvae are practically always found attached in the 

 left sac, and it is the opinion of Dr. Guyot that this portion affords 

 the most stable point for larval attachment. He thinks that cases 

 are exceptional in which larvae maintain themselves in the right sac. 

 This, however, does not explain the attachment of G. nasalis in the 

 duodenum and to the walls of the pharynx, nor does it account for 

 the attachment of G. haemorrhoidalis in the right sac of the stomach, 

 in the duodenum, or in the rectum. As has been mentioned by 

 Dr. Guyot, the reason for attachment in certain regions of the diges- 

 tive tract will remain a mystery until the manner in which larvae 

 are nourished is ascertained. 



Various investigators have been unable to discover white or red 

 corpuscles of the horse in the pharynx and other alimentar} 7 portions 

 of the larvae. Clark believed their food was probably the chyle, but 

 Guyot rejects this explanation, as larvae in the pharynx are located 

 where this could not possibly be utilized. As Oestrus oris larvae 

 nourish themselves with the mucus secreted by the mucosa of the 

 nose and frontal sinuses of sheep, and as those of Hypoderma utilize 

 the pus of the abscesses which the} 7 create by their presence in cattle, 

 he believes it permissible to suppose that those of Gastrophilus find 

 nutriment in the inflammatory products of the gastric mucosa. 



It would appear, from observations, that Gastrophilus larvae some- 

 times feed upon the blood of the animal, although they are not de- 

 pendent upon it for subsistence. The red and maroon color of G. 

 intestinalis and G. hceinorrhoidalis, with their attachment upon 

 points other than the mucosa of the left sac, would bear out this 

 hypothesis, which is further supported by the fact that G. haemor- 

 r/io'idalis when fully developed in the rectum still retains a pinkish 

 color. 



THE ALVEOLAR LESIONS OF THE STOMACH. 



In Dr. Guyot's examinations of lesions caused by the attachment 

 of larvae to the mucosa of the left sac, the muscular coat was not 

 damaged. The condition found was merely a localized inflammation 

 around the point of larval attachment, in which the derma had been 

 invaded by leucocytes. He assumes that this is only the common 

 inflammatory reaction which would be normally produced around 

 any foreign body. 



In following these studies Perroncito found that the bottom of the 

 alveolus varied in size and became the seat of a more or less remark- 

 able inflammatory process. This produced a thickening of the walls 

 of the stomach and finally the disappearance of the muscular tissue, 

 which becomes hard and compact, preventing the normal functions of 



