Journal of Applied Microscopy. 



281 



Improved Movement for Microtome Knife. — I have made an addition 

 to my student microtomes and also to the laboratory form, which I think is an 

 advantage. I have met with two difficulties in using the microtome : first, the 

 pressure of one's hand on the knife block caused the knife to change the thick- 

 ness of the slice being cut ; and second, in case the block of tissue presented 



Top view of microtome with lever for moving knife block. 



structure harder in one part than another, the knife could not be carried steadily 

 through the whole of a section. In order to overcome the first, the knife block 

 should be pulled in a perfectly horizontal direction, with no chance of any 

 greater or lesser pressure downward on the way, and by using a lever with the 

 power-arm five or six times as long as the arm attached to the knife block a 

 steady motion of the knife could be secured. 



End view of microtome showing relation of lever to knife. 



The arrangement has been a very helpful one, both in my own hands and in 

 those of my students. Thos. D. Biscoe. 



Marietta College, Ohio. 



Blood Plates. — An easy and sure way to procure preparations of those 

 enigmatical bodies known as blood plates, is to place a drop of one per cent, 

 solution of osmic acid upon the hand and with a flamed needle make a puncture 

 through the drop of acid. The blood follows the needle and can be forced into 



