149 



ulcer and bleeding surface, the infestation usually occurring while 

 the victim is sleeping in some exposed place, such as woods, jungle 

 and unscreened houses. The nasal cavity is the favourite and most 

 dangerous point of attack especially in persons subject to nose-bleeding, 

 or suffering from nasal catarrh with an offensive discharge. The fly, 

 which has a very keen sense of smell, oviposits in the nostril, into 

 which the young screw-worms further migrate, tearing the mucous 

 membrane and feeding on the resulting blood and serum. They 

 soon penetrate into the sinuses of the nasal fossae, where, with plenty 

 of liquid food, warm temperature and a constant supply of fresh air, 

 they grow rapidly, devouring the lining membranes and burrowing 

 into the surrounding muscles and cartilages. 



In but few of the many cases of human myiasis caused by C. macel- 

 laria and reported from the United States and Central and South 

 America does the patient remember having been attacked by flies, but 

 since a mass of 100 eggs is about the size of a small pea it is highly 

 improbable that he could have been unaware of their presence until 

 they hatched out, except under certain conditions. Such conditions 

 are those of : — (1) a person falling asleep in the late afternoon or 

 early evening and sleeping till morning, thus allowing time for eggs 

 to be deposited and hatch, and the larvae to ascend into the nostrils ; 

 (2) an intoxicated person lying out of doors in a drunken stupor for 

 several hours ; (3) a person suffering from nose bleeding being uncon- 

 scious of the presence of eggs if deposited in a blood-clot ; (4) a person 

 suffering from leprosy or any other disease liable to give rise to anaes- 

 thesia of the nasal mucous membrane, in which case the first intimation 

 of infestation would be due to the larvae burrowing into sound tissue. 

 In the interior, cases which terminate fatally are not uncommon 

 among the natives, and in these, infestation has usually occurred 

 when the individual was returning from some, place where he had 

 been drinking heavily. 



Aural myiasis is somewhat less frequent than nasal, but does occur 

 in the case of infants, and persons with a discharging affection of 

 the ear, causing considerable suffering and sometimes death. 



Infestation of the genitalia takes place occasionally, usually in the 

 case of naked children or of old people suffering from senile decay who 

 cannot keep themselves always properly protected with clothing, 

 while a case of umbiUcal myiasis has been met with, the subject being 

 a Spanish labourer. 



All kinds of domestic animals are subject to attack by this fly, 

 cases being recorded of a deerhound belonging to a hunting pack, 

 which became infested, w^th the resultant loss of bones and teeth 

 in the right upper jaw and the sense of smell ; also of three tame 

 deer kept in a laboratory yard. Cats are practically immune, owing 

 to their habit of constantly licking and cleaning their wounds. 



Experiments to investigate the depth at which larvae in carcases 

 may be buried and still emerge as flies, showed that 56 per cent., 

 mostly females, emerged when buried at a depth of 2| ft. , the number 

 emerging from a lesser depth being of course proportionately greater. 



No positive proof is yet forthcoming of C. macellaria being a disease- 

 transmitting agent, but research is necessary into its power of trans- 

 mitting anthrax among cattle. Reasoning from the facts that a 

 thin blood-stained fluid is ejected from the mouth and nostrils at 



