VETERINARY MEDICINE. 85 



and the troatment once repeated 7 or more days later, the only injury to 

 be expected as a rule being more or less epidermal exfoliation, and sometimes 

 slight soreness or tenderness of the skin, local in character." 



The experiments fully confirmed the observations of various investigators 

 and practical users of arsenical dips who have found that ticks are very 

 sensitive to arsenic. Little is known, however, as to the aveuue by which the 

 arsenic enters the body of the ticks. After treatment with an arsenical dip 

 the vast majority of the young adult females die before they reach the engorged 

 stage, and the younger they are the less likely are they to survive and become 

 engorged. 



" In G experiments the cattle were found to be free from engorged ticks 3 to 

 5 days after the first treatment, in 4 other experiments they wei-e free 7 to 9 

 days after treatment, in another they wex'e nearly free 5 days after treatment, 

 in another experiment all that were examined were free from engorge<l ticks 8 

 days after treatment, and in 2 other experiments the cattle were nearly free 

 from engoi-ged ticks 8 days after ti'eatraent." 



In order to obtain data bearing upon the question of the fate of ticks which 

 reach engoi-gement and fall from cattle subsequent to dipping, engorged ticks 

 were collected from the cattle in the various experiments immediately after 

 treatment and on successive days thereafter and kept under observation. 

 "Whereas in many of the lots from treated cattle all of the ticks died without 

 ovipositing, in most cases some of the ticks deix)sited eggs, the percentage of 

 ticks ovipositing usually being low, although in rare instances as high as 

 100 per cent." Ticks from treated cattle which survived to deposit eggs nenrly 

 always deposited a much smaller number than ticks from untreated cattle, and 

 moreover, they rarely hatched. Out of approximately 70 lots of ticks from 

 treated cattle, only 4 lots deposited eggs which hatched. 



" Judging from these results it would appear that the hatching of eggs de- 

 posited by ticks which survived treatment with arsenical dips is a rather rare 

 occurrence. Furthermore, it has been noted Ihat the larvjB from eggs deposited 

 by females which have been subjected to arsenical solutions are frequently in 

 such a weakened condition that they can not emerge from the eggshell, or they 

 may become lodged in the opening of the ruptured shell and fail to extricate 

 themselves, or show such slowness of movements after emerging as to make one 

 believe that they could not effect a successful attachment after reaching a host, 

 a condition of the larvae which has also been noticed in the case of eggs sub- 

 jected to unfavorable conditions, such as low relative humidity and low 

 temperatui'es." 



The data relative to the ticks removed from cattle after treatment and their 

 corresponding control from untreated cattle, and to engorged ticks dipped in the 

 laboratory, are presented in tabular form. 



" Very few male ticks were found alive on cattle later than a day or two after 

 treatment, and it is probable that most of these were ticks which were in the 

 nymphal stage at the time of treatment. It may therefore be concluded that 

 arsenical dips are highly eflicacious so far as the destruction of male ticks is 

 concerned. . . . The vast majority of nymphs were killed by a single treat- 

 ment. In several experiments, however, some of the nymphs survived and 

 afterwards molted. ... No instance was observed in any of the experiments 

 of the survival of ticks in the larval stage after a single treatment with an 

 arsenical dip." 



The bulletin concludes with a discussion of the j>ractical significance of results 

 of experiments with arsenical dips, taking up the composition of the dip, 

 method number, and frequency of applications, and handling the cattle. 



A plan is given for a draining pen for cattle after dipping. 



