150 MEDICAL ZOOLOGY. 



injurious to pear-trees, and has been collected and used medicinally with most 

 excellent effect. 



Lytta contains, besides the vesicatoria of Europe, many species in all 

 parts of the world, and all the species thus far tried have proved efficacious. 

 In our own country every section affords species, and many are large and 

 beautiful. 



Lytta nuttalli is a very abundant species on the plains and in Oregon. It 

 resembles the vesicatoria so closely as to have been mistaken for it. It was 

 reported by one of the early government expeditions that bushels could have 

 been collected at one place, and that many were swept up and destroyed to 

 afford room for camping purposes. This is no exaggeration, as I have seen, 

 in Calfornia, many hundreds of thousands that could have been gathered in 

 very few minutes. Lytta nuttalli could readily be substituted for the vesica- 

 toria and would defy detection either by the color of the powder or by its 

 effects. 



Lytta vulnerat'a and melcena are found in California and are those spoken 

 of above. Numerous experiments have been tried with them, internally and 

 externally, and the full effect of the medicine produced. Many species could 

 be enumerated from all parts of our territory, but as they all possess the 

 same qualities, the few above named will suffice. 



Tegrodera erosa is a beautiful species found in California, the head and 

 thorax red and elytra yellow with two black bands, one terminal, the other 

 median ; the surface is eroded or with a raised network. 



SEAT OF VESICATING POWER. 



This matter has long been the subject of conjecture, and to Prof. Joseph 

 Leidy is due the credit of experimenting with more satisfactory results than 

 any preceding investigator. Cantharidin had long been known as the active 

 agent, even before these experiments. A full account is published in the 

 Am. Jour. Med. Sciences for Jan. 1860, and Jour. Pharmacy, March, 1860. 

 In these papers it will be found that the blood is the most effective, then 

 certain glands or appendages of the generative system, and finally the eggs. 

 From this it will be seen that the greater portion of the body, if deprived of 

 blood, would be totally inert. The power of the blood may be realized by 

 any one collecting these insects. They have the habit of causing the rup- 

 ture of certain of their ligaments, particularly at the knee-joint, from which 

 a drop will issue capable of producing a large blister on tender skin. The 

 question has occasionally been raised as to whether certain of our species 

 did not produce more unpleasant effects on its external application than the 

 foreign one. There can be but little truth in such suppositions. I have used 

 very many of our native species medicinally, and have experimented on my 

 own person with many others, and can notice no difference. There can be 

 no doubt that our natives are at times the more active and rapid in action. 

 This can be attributed to the freshness of the specimens made use of, as the 

 imported article, particularly in powder, is apt to deteriorate. 



