36 THE ROUNDWORMS OF DOMESTIC SWINE. 



bacillus is normally found in the stomachs of hogs and other animals, 

 and while under ordinary circumstances it has no pathological effect, 

 if enabled through some lesion to the mucous membrane to gain 

 access to impaired tissue, its proliferation results in the sloughing of 

 the mucous membrane and the formation of ulcers. 



Mohler and Morse (1904), describing necrobacillosis of the digest- 

 ive tract, state: "The necropsy in such cases revealed hemorrhages 

 and erosions in the stomach, but no areas of coagulation, ' ' an accurate 

 description of the conditions found by the present writer. The char- 

 acteristic odor described for lesions of Bacillus necrophorus was only 

 faintly present, being modified perhaps by the boric acid with which 

 the specimen was sprinkled and which may account for the paucity 

 of the parasitic flora found. 



How deeply Arduenna strongylina is capable of penetrating into the 

 submucosa was well shown in one of the specimens forwarded from 

 Chicago. A piece of the cardiac portion of the stomach contained 

 a worm 12 mm. long which had bored diagonally into the mucosa to a 

 depth of 10 mm., only the caudal end projecting above the "surf ace. 

 The hole made was similar to a pin prick, a simile used by Von Ratz 

 (1899d) in describing the lesions observed by him. Indeed Von 

 Ratz's description is practically identical with the conditions found 

 by the present writer. 



The habit of boring into the mucosa characteristic of these para- 

 sites would seem an ideal method of inoculating the submucosa of the 

 host with Bacillus necrophorus if any were present, and this, consid- 

 ered in connection with the conditions observed in infested stomachs, 

 indicates that the worms may be the indirect cause of grave ulcera- 

 tion. Considered apart from their possible r61e as infective agents, 

 the mechanical injury to the stomach walls due to the penetration of 

 the worms in numbers would seem to be a serious factor even if the 

 worms were unassociated with bacilli. Moreover, the livid red color 

 of the worms in situ in the stomachs examined would seem to indicate 

 that they feed on blood, an additional reason for regarding them as 

 dangerous parasites. The whole question, however, of the patho- 

 genicity of the parasites, and as to their relationship to the lesions 

 observed, remains open for further investigation. 



An examination of the stomach portions received showed specimens 

 of Physocephalus sexalatus attached in the same manner as already 

 noted for Arduenna strongylina; hence the former parasite may be 

 considered only less dangerous than the latter, as it is less abundant. 



LIFE HISTORY. 



Nothing is known in regard to the development of the worms from 

 the egg to the adult. The wide distribution, the frequency of the 

 parasites, and the similarity of the eggshell to that of an ascarid, 



