KiO GYPSY AND BROWN-TAIL MOTHS. [Jan. 



upon a small area of the skin of the upper arm. This was followed by 

 the appearance of numerous minute red spots. There was a slight sore- 

 ness over this area, suggestive of the presence of minute foreign bodies 

 in the skin. The red spots persisted for twenty-four hours or more. 



The tufts on the back of a tussock moth caterpillar (Orgyia leuco- 

 >//// a) were examined, and found to consist of long, sharp-pointed hairs, 

 with sharp barbs projecting at intervals along their entire length. These 

 hairs were of the same general type as the nettling hairs of the brown- 

 tail moth, but were many times as long. When such hairs from the 

 tussock moth caterpillar were nibbed upon the skin, several minute red- 

 dish points appeared. There was a barely perceptible prickling sensa- 

 tion, but no itching. Another person inoculated in a similar manner 

 showed no lesion whatever. Thus neither finely comminuted glass wool 

 imr the sharp-pointed, barbed hairs of a tussock moth caterpillar when 

 rubbed into the skin produced any process resembling in character the 

 brown-tail moth dermatitis. 



At this time the accidental discovery of a peculiar reaction, which takes 

 place when the nettling hairs of the brown-tail moth are mingled with 

 blood, indicated the presence of a soluble chemical substance in connec- 

 tion with them. If a number of nettling hairs are placed in a drop of 

 blood between a slide and cover glass, an immediate change takes place 

 in the red blood corpuscles. They at once become coarsely crenated, 

 and the rouleaux are broken up in the vicinity of the hair. The cor- 

 puscles decrease in size, the coarse crenations are transformed into 

 slender spines which rapidly disappear, leaving the corpuscles in the 

 form of spheres, the light refraction of which contrasts them sharply 

 with the normal corpuscles. The change of form, in addition to a slight 

 shrinkage, causes the red blood corpuscles to appear much smaller than 

 normal. This reaction takes place so rapidly when the fresh, active 

 nettling hairs are used, that the eye can not follow its various stages. 

 However, by treating these hairs in various ways the time of this re- 

 action may be retarded so that all stages of transformation may be seen. 

 The reaction always begins at the basal sharp point of the hair. It was 

 thought that this might possibly be a purely physical phenomenon, but 

 this is disproved in various ways. A variety of minute foreign bodies 

 were mingled with (lie blood in a similar manner. Such material as 

 minute particles of glass woo], the barbed hail's of the caterpillar of a 

 tussock- moth and the other coarser hairs of the brown-tail all failed to 

 produce any effect on the red blood corpuscles. 



The next step was to determine whether the nettling hairs could be 

 inactivated by heating. After baking for one hour at 100 f., they 

 _rave a typical reaction with red blond corpuscles, and produced a der- 

 matitis when rubbed upon (lie skin. Baked for one hour at 110 ('., 

 they still ua\c the typical reaction with red blood corpuscles, and pro- 

 duced ,-i typical dermatitis when rubbed upon the skin. However, after 

 beiii'_r baked an hour at 115 ('.. the nettling hairs no longer affected 



