12 Roosevelt Wild Life Bulletin 



many of them fled from them in real terror. It was found, however, 

 particularly among the older girls, that a little instruction in the real 

 nature of the animals, their essential harmlessness and their beauty 

 and gracefulness, did much to calm these fears and to arouse interest. 

 In some cases aquaria were placed in the camps and the study of 

 leeches became a regular part of the natural history lessons. 



The frequency of the bites was much less than had been anticipated 

 from early reports. Very rarely is any one child attacked by 

 more than a single leech, and it is seldom that as many as three or 

 four out of a group of fifty or so swimming at one time will be 

 bitten. For all the camps throughout the season the total number 

 bitten daily would scarcely average ten. Altogether the actual problem 

 seems not very urgent. Nevertheless it presents some aspects of 

 interest and its potential importance renders its solution desirable. 

 Some of these aspects may profitably be considered. 



A usual effect of a leech's bite is a more or less intense and pro- 

 longed itching, which probably results from the injection into the 

 wound of a natural haemolytic agent in the saliva. If the leech be 

 permitted to complete its meal this substance is largely or entirely 

 withdrawn from the wound, but if the meal be curtailed much of the 

 haemolysin remains and acts as an irritant. Some persons are much 

 more sensitive to the irritant qualities of leech bites than others, just 

 as some are more sensitive to the poison of the bites of mosquitoes 

 or other insects. To allay the itching a styptic pencil such as the 

 barbers use, weak ammonia water, or witch-hazel extract may be 

 applied with benefit. This is desirable, as scratching with dirty finger- 

 nails may lead to infection of the wound, and apparently this entirely 

 secondary effect is the chief source of injuries complained of, as in 

 the case of many biting insects. 



The hagmolysin prevents coagulation of the blood, which is the 

 reason why a leech bite continues to bleed so much longer than an 

 ordinary slight cut. The styptic pencil is the readiest means of 

 stopping the hemorrhage. In tihe case of hgemophilics or " natural 

 bleeders," like the girl mentioned above, whose blood does not readily 

 coagulate, the addition of a further deterrent may cause the 

 hemorrhage from even so minute a wound as a leech bite to become 

 a possibly serious matter. Fortunately, such persons are rare. 



The species of leech under consideration will draw at a meal about 

 two to two and one-half times its weight of blood, while the European 

 medicinal leech is reported to take from four to seven or even ten 

 times its weight. As the usual weight of the leech in Carr Pond 

 runs between three and five grams it is apparent that the amount of 

 blood extracted from a vigorous child by one or even several leeches 

 is negligible. Very rarely indeed does a child lose as much as one- 

 half ounce of blood. It is obvious, however, that if many large and 

 vigorous leeches should simultaneously attack a small, weakling child 

 the resulting loss of blood might entail serious consequences. Many 

 of the children attending these camps are ill-nourished, anaemic, and 

 little able to afford any considerable loss of blood. Fortunately, 

 from this point of view the leeches are present in the Palisades 



