﻿THE CATTLE GRUBS OR OX WARBLES 51 



The occurrence of larvse, varying considerably in size, on the 

 surface of various abdominal organs has been noted by a number 

 of investigators. For instance, Koch {53) records having found 

 larvae on the pleural side of the gullet as well as under the mucous 

 coats; on the surface of the spleen; some on the paunch and one 

 between the muscular and mucous layers of it; a few among the 

 intestines; and some in the connective tissue of the thoracic cavity 

 just below the vertebral column. Home (45) has on several oc- 

 casions observed several larv^ in the connective tissue around the 

 kidneys, and Had wen and Fulton {^O) have observed several 

 larvse on the pericardium. Berg (3) has found larvae in the con- 

 nective tissue between the small loin muscles and the muscle of 

 the hip, and Koch (53) has obsei*ved a single larva in the inter- 

 muscular tissue of the back. Many writers have recorded the 

 finding of larvae, sometimes in considerable numbers, in the spinal 

 column throughout the greater portion of its length and also pass- 

 ing through the posterior foramina. Hadwen and Bruce {38) 

 state that larvae observed by them in the spinal canal were found 

 in the areolar tissue which surrounds the dura mater. Their 

 presence was accompanied by evidences of green pigmentation and 

 gelatinous infiltration at different points along the cord. 



In the writers' own work they have encountered larvae in nearly 

 all of the locations where they have been reported by others. It is 



Fig. 24. — Hypoderma lineatum: Diagram showing: position, dirpction of travel, and 

 length of larvae in millimeters in gullet of calf (No. 22) 



not at all uncommon for the larvae to be present just under the 

 pleura along the esophagus. The larvae found in that region were 

 practically of the same size as those in the submucous connective 

 tissue of the gullet. Wide distribution of the larvae within the ab- 

 dominal cavity has been noted in the case of the experimental ani- 

 mals infested at one definite period, indicating that there is a general 

 scattering of the larvje of the same age. On account of the interest- 

 ing distribution of the larvae observed in experimental calf No. 22 

 the location of the larvae will be briefly summarized. This animal 

 had about ?>00 eggs deposited upon it by flies on JNTarch 22 and 28. 

 Most of these were laid in the region of the dewclaws on the hind 

 legs. On Julv 3 the animal was killed and carefully dissected. In 

 the connective tissue beneath tlie mucous lining of the gullet 17 

 laiwffi weie found. One of these was crushed and its position not 

 noted. The position of tliese larva? in tlie gullet and direction they 

 wei-e headed are sliown in P'igure 24. Their size ranged from H.G 

 to 6 millinieters in length, the average being 5.-3 millimeters. On 

 the paunr-li 12 larva' were found. Six of tliese weie aluiosl irnmedi- 

 ately under ihe spleen, but none were attached to tha< organ when it 

 was peeled off. The other six were scattered over the i-iinicn at 

 widely vai-ying distances from the gullet entiance. Tliese liingcd ui 

 size from h.H to H millimeters, witli an average of (l.H millinieters. 

 Some of these had the anterior end pointing toward the gullet en- 

 trance, otheis were pointing directly away from it, and others were 



