454 Gastrophilus Larvae in the Stomach of the Horse. 



are thirteen to fifteen mm. long and live exclusively in tlie jiylorie, portion of the 

 stomach and in the duodenum. 



5. Gastrophilus flavipes occurs around the Mediterranean; the larvie are par- 

 asitic in the stomach of the donkej. 



Pathogenesis. Bot-fly larvae may be present in the stom- 

 ach, even in considerable numbers, without disturbing its func- 

 tion markedly ; this may be due to the fact that they are most 

 commonly adherent to the left half of the stomach which plays 

 no important role in the digestive function. If, however, they 

 are present in very considerable nimibers and bore into the 

 glandular right half of the mucosa, they then cause pain to 

 their host and bring about nutritive disturbances. This is 

 partly on account of the withdrawal of blood and lyiuph but 

 mostly on account of disturbances of the motor and secretory 

 function of the stomach. Whether the hemolytic substances 

 which Weinberg has found in the larvae have a deleterious 

 effect upon the blood of the host is not known. The pylorus 

 or duodenum may exceptionally be obstructed by the larvae. 



In the neighborhood of the defects which they have pro- 

 duced in the gastric mucosa, the larvae cause a chronic inflam- 

 matory process by poisonous metabolic products and by me- 

 chanical irritation. When the loss of substance is very consid- 

 erable, the power of resistance of the gastric wall is very much 

 decreased and an accumulation of gastric contents may easier 

 occur. In exceptional cases the larvae may perforate the wall 

 of the stomach or even that of the duodenum (Numan), or some 

 larger blood vessel is injured and hemorrhages may occur, which 

 may have a fatal termination (Ziirn, Dammann, Hertwig, Bruck- 

 miiiler, Thomas). As to the pathogenic effect, the larvae adher- 

 ing to the pylorus and the duodenum are the most dangerous 

 (G. haemorrhoidalis and nasalis). 



The ulcers caused by gastrophilus larvie may, like any other loss of substance, 

 form the portal of entrance for various infectious microorganisms (Perroncito). 



Anatomical Changes. On postmortem examination, one 

 finds the larvae in the stomach and sometimes in very great 

 numbers. Numan counted more than 1,000 in one case; Ker- 

 sten found over five quarts in another case; Rexilius saw the 

 stomach and the constricted duodenum filled ^^dth larvae, and 

 Kater the duodenum completely obstructed with gastrophilus 

 larvae. On the internal surface of the gastric wall one sees 

 round, craterlike depressions with a diameter of 3-4 mm. ; the 

 base appears red, and the margins are formed by the thickened 

 epithelial covering of the mucosa. In the glandular portion and 

 in the mucosa of the duodenum one sees around the place of at- 

 tachment swelling, redness and possibly also small hemorrhages. 

 Exceptionally there may be abscesses in the gastric wall. 



According to Petit and Germain the base of the ulcers is formed by necrotic 

 tissue; in the neighborhood of the latter are chronic inflammatory changes with 

 infiltrating eosinophilic cells; small pegs of epithelial cells penetrate into the under- 



