BY T. HARVEY JOHNSTON AND M. J. BANCROFT. 307 



Of is more evident owing to the shortness of the hair. These 

 drops become thick and sticky, ultimately forming little 

 granular masses or thin flat yellow scabs, according to the 

 size of the original drop. The largest patches seen were about 

 the size of a sixpence or slightly larger. In some animals 

 these little masses of exudate are perfectly clear, the skin 

 appearing through them quite uninflamed. In others 

 some blood may be present, then the resultant scab is 

 discoloured. When dry these scabs are readily flaked off 

 leaving a rounded area of smooth clean skin beneath. There 

 is no positive evidence to prove that each patch of exudate 

 is caused by the bite of a tick, though, occasionally, larval 

 ticks have been found attached to a dry scab having become 

 entangled in the sticky fluid. This exudation of lymph 

 must be due to one or both of two causes (1) either a slight 

 mechanical injury to the tissue which, while not penetrat- 

 ing a blood capillary, allows an escape of lymph from the 

 tissues ; such might be caused by the larval tick inserting 

 its rostrum, and then withdrawing it and going elsewhere ;. 

 or (2) to an increase in blood pressure, involving an extra- 

 vasation of lymph from the capillaries. The formatioa 

 of small hard lumps on the flanks, and in the vicinity of 

 the escutcheon and neck of resistant animals, upon the 

 centre of which a patch of fresh exudate may or may not 

 appear, would be accounted for by an increase in blood 

 pressure, since when scored, blood flows very freely from 

 such lumjDs. The affected area is rather irritable, the cowa 

 shewing a desire to lick or rub the part. 



Mr. Hull has found that this exudate is in abeyance 

 during the winter months. Notes taken from his letters 

 shew that this phenomenon is most likely to occur during the 

 months October-June. In 1916, his last record of its- 

 occurrence before the winter, was on June 2-ith, when one 

 of us examined the animals, exudate being then abundant. 

 The first record of it in the following spring was on October 

 20th, when exudate was present in small patches. In the 

 beginning of the next month, during some humid weather, 

 it appeared abundantlj'. The cows were in splendid con- 

 dition and no ticks had been noticed on them. Records 

 of the occurrence of the exudate came to hand from time 

 to time up till April 28th, 1917, although little or none 



