HVPODERMO.SIS IN THE OX (WARBLES). 



647 



The female deposits her eggs on animals with fine skins. These 

 eggs are elliptical, and provided with a kind of tail of a brownish 

 colom-. They soon become converted into larvre, provided with rows 

 of little spines. 



The manner in which the eggs are laid is not exactly understood, 

 nor are we better informed regarding the hatching of the young larvae. 

 Until recently it was believed that the larva perforated the skin as soon 

 as it quitted the egg, and then penetrated as far as the subcutaneous 

 connective tissue, liecent observations, however, have upset this view. 

 It is probable that this larva, like other gastrophili, is swallowed by 

 animals of the bovine species, and passes through the intestine into 

 the surrounding tissues by a path which is yet unknown, possibly by 

 the blood-vessels, whence it makes its way after a longer or shorter 

 interval into the subcutaneous connective tissue. 



Certain recent observations seem to support the latter view, which 



•V^ 



Fig. 265.— a, Hypotlenna bovis, natural size. V>, larva of the hypoderma 

 escaping from a " warble." (After liailliet.) 



is also corroborated by known facts regarding hypodermic myiosis 

 in man. The eggs are laid in summer, and the swellings indicating 

 the presence of the larvffi only appear during the winter. Henrichsen 

 found young larvte in the fatty tissue situated between the periosteum 

 and spinal dura-mater, between the period from December to March. 



Symptoms. Whatever the mode of development of the larva?, 

 cutaneous swellings appear between the months of February and 

 March on the back, lumbar region, quarters, shoulders and ribs, and, 

 less frequently, over the chest, belly and thighs. 



They vary in number. Commonly there are from ten to twenty, 

 and it is only in rare cases that less than four or five are found. As 

 soon as they attain the subcutaneous connective tissue they act as 

 foreign bodies, causing a circumscribed inflammation, and finally sup- 

 puration In this way the so-called " warbles " are produced. 



