STRONGYLIX.E 289 



2. Strongylus edentatus (Sclerostomum edentatum). Strongylinae 

 (p. 280).— The head is globular. The Ixiccal capsule is goblet-like, and 

 teeth are absent. The bursa of the male is similar to that of Strongylus 

 equinus. The vulva of the female is near the posterior third of the body. 



The female is 33-36 mm. (1 5/16-1 7 16 inches) in length; male, 23- 

 25 mm. (7/8-1 inch). 



The eggs are oval and in dimensions about as in Stro7igylus equinus. 



As adults these worms are parasitic in the cecum and colon of the 

 horse; as larvie in the abdominal and thoracic organs. 



3. Strongylus vulgaris (Sclerostomum vulgare). Strongylinse (p. 

 280). — The buccal capsule is shallow and has a single tooth at its base, 

 prominent projections causing the tooth to appear as two. The bursa 

 of the male has three lobes, the median one overlapped by the two 

 lateral. The vulva of the female is near the posterior third of the body. 



The female is 24 mm. (15/16 of an inch) in length; male, 15 mm. 

 (5/8 of an inch). 



The eggs are as in the preceding species. 



Parasitic as adults in the cecum and colon and in immature stages in 

 the mesenteric blood vessels of the horse. 



4. Cylicostomum tetracanthum (Sclerostomum tetracanthum). 

 Strongylime (p. 280). — A white or reddish wiiitc worm, attenuated 

 antcriorl}', the mouth surrounded l)y a cuticular fold. The buccal 

 capsule is armed Avith a crown of triangular teeth. The vulva of the 

 female is just anterior to the anus. 



The female is 10-18 mm. (3/8-11, 16 of an inch) in length; male, 8- 

 12 mm. (5/16-1/2 an inch). 



The eggs are oval, 100 microns in length by 47 microns in breadth. 



Parasitic in the cecum and colon of the horse. 



Development. — The worms causing sclerostomiasis of the horse 

 were formerly grouped under the name Strongylus armafiis. According 

 to Looss (1902) it is the innnature stages of the species Strongylus vul- 

 garis (Looss, 1900) which are concerned in the production of verminous 

 aneurysms in the mesenteric arteries of the horse. M. Neveu-Lemaire 

 (Parasitologic des Animaux Domestiques, 1912) describes the worm 

 responsible for these lesions under the name Strongylus equinus. 



This worm when mature lives in the cecum and colon where it firmly 

 attaches to the mucosa by its Ijuccal armature. In its agamous state it is 

 found in subnuicous cysts of these organs and in aneurysms of the 

 mesenteric artery. According to the investigations of Railliet the eggs, 

 which are deposited in the cecum and colon and expelled with the feces, 

 may develop in a few days if they meet with moisture at a temperature 

 of 12° to 25° C. (53° to 77° F.). The hatched embryos, if they continue 

 amid favorable conditions, grow, molt, and acquire a great vitality. It 

 is at this stage that they are ingested by the equine host with the drink- 



l/ 



