348 THE AMERICAN MONTHLY [Dec 



erally require soaking in a ten per cent solution of so- 

 dium of potassium hydrate (caustic potash), for periods 

 varying from an hour or two up to a week. Too much 

 soaking will destroy the object and also render it too trans- 

 parant after mounting, whilst too little may leave it hard 

 and difficult to deal with. A little thought and attention 

 will therefore be necessary, and a slight pressure with a 

 blunt needle will tell whether the object is sufficiently 

 soaked. In the case of large insects, like cockroaches, we 

 should soak them for several days until they begin to give 

 off an unpleasant smell. The alkali must then be removd 

 by soaking in several changes of clean water. The inside 

 of the insect can be got rid of by gentle treatment with 

 the camel-hair brushes. Plant subjects are best softened 

 by long soaking in water. 



Parasites in the Blood. — Dr. Leon S. Le Wald, of 

 New York City, spoke on this subject, dwelling particu- 

 larly on the very recent interesting experiments in regard 

 to the relation of mosquitos to malaria. He said that Drs. 

 Manson and Ross, of England, had proved within the last 

 month most conclusively that malaria was transmitted to 

 the human subject by mosquitos. Mosquitos raised in the 

 laboratory, and known to be free from malarial infection, 

 were allowed to suck the blood of a person in Italy suf- 

 fering from malaria, the type of which had been determ- 

 ined by microscopical examination of the blood and iden- 

 tification of its contained parasites. These mosquitos 

 were then sent to London and allowed to bite Dr. Man- 

 son's son, a young man who was perfectly healthy at the 

 time, and free from malaria infection. He promptly de- 

 veloped, on September 13, 1900, the characteristic signs 

 of true malaria, and examination of his blood on Septem- 

 ber 16th showed many tertian parasites — the same form 

 present in the blood of the Italian. After a few days, qui- 

 nine was administered freely, and in two daysmore these 



