CUTANEOUS BOTS 515 



is plugged by the posterior end of the maggot, and used for ob- 

 taining air. At intervals these warble-like boils give rise to the 

 most excruciating pain, due, no doubt, to a turning over or 

 moving about of the spiny larva in its close quarters. 



There are very conflicting records of the time required for the 

 larvsB to reach maturity, but it seems probable that at least a 

 month or six weeks is usually occupied. When mature the larvae 

 voluntarily leave their host and fall to the ground to pupate. 

 They transform into the adult form in the course of several weeks. 



The swellings under the skin occupied by human botflies, as 

 remarked before, are very painful at intervals, while at other 

 times they are entirely painless. As the larva matures, a puslike 

 material exudes from the open end of the " boil," containing, 

 no doubt, the excretions of the maggot. After the worm has 

 evacuated its cyst or has been removed the wounds sometimes 

 become infected, and may even result in blood poisoning and 



death. 



The method usually employed to remove the maggots is to 

 apply tobacco juice or tobacco ashes to the infested spots, thus 

 killing the worms and making their extraction easy. Another 

 method used by natives in some parts of South America is to tie 

 a piece of fat tightly over the entrance to the boil. The larva, 

 deprived of air, works its way out into the fat, being thus induced 

 to extract itself. A much more satisfactory method of deahng 

 with the worms is to kill them with an injection of weak carbolic 

 acid, mercuric bichloride, or some other poisonous substance, 

 then enlarge the entrance to the cyst with a sharp clean knife 

 and remove the body of the worm. A washing of the wound 

 with a weak carbolic or lysol solution, followed by an antiseptic 

 dressing, obviates any danger of subsequent infection. The 

 wound heals quickly but leaves a scar. 



Other Bots. — Other botflies occasionally infest man and cause 

 cutaneous myiasis. The common warble-flies of cattle. Hypo- 

 derma lineata and H. bovis (Fig. 247), have been recorded as oc- 

 curring in the skin or flesh of human beings and there is one fatal 

 case on record where an ox warble caused an ulceration in the 

 back part of the lower jaw of a boy six years old. Ox warbles 

 usually gain access to the tissue under the skin of cattle in an in- 

 direct way, the hairy bee-like flies depositing their eggs on hairs 

 of cattle where they will be licked off. As soon as licked the 



