312 THE AMERICAN MONTHLY [Sept. 



MICROSCOPICAL MANIPULATION. 



On the use of Turpentine in Microscopic Work. — Hav- 

 ing- lost several carefully prepared specimens of insects 

 by using" as a final clearing- agent the ordinary turpentine 

 of the shops, I was led to inquire into the matter, when I 

 found that the trade article is not the turpentine referred 

 to in Davis' "Practical Microscopy," p. 415, and Carpen- 

 ter's "The Microscope," pp. 441 and 442 (1891 edition). 

 It is the natural balsam which flows from the trees that is 

 referred to, and not the distilled extract sold as turpentine 

 or oil of tunpentine. 



The following definition is taken from Cooley's "Cyclo- 

 paedia of Practical Receipts" (1892 edition), p. 1720 : — 

 "Turpentine, Turpentin, Terebinthina — an oleo-resin 

 flowing- from the trunk (the bark being- removed) of Pinus 

 palustris, P. taeda, P. sylvesteris, and various species of 

 Pinus and Abies. It is viscid, of the consistence of honey, 

 and transparent. By distillation it is resolved into oil of 

 turpentine, which passes over into the receiver, and into 

 resin, which remains in the still. Bordeaux, or French, 

 turpentine is from P. maritima. Chian turpentine is from 

 P. terebinthus. It is pale, aromatic, frag-rant, and has a 

 warm taste devoid of bitterness. It is much adulterated, 

 and a fictitious article is very g-enerally sold for it. Venice 

 turpentine is the liquid resinous exudation from the Abies 

 larix. It is sweeter and less resinous tasted than common 

 turpentine, but is now scarcely ever met with in trade. 

 That of the shops is wholly a fictitious article." 



In Carpenter, p. 442 (1891 edition), it is stated that the 

 natural balsam has a peculiar power of rendering- the chit- 

 inous textures of insects transparent. — Victorian Naturalist. 



Counting Blood-Corpuscles. — Dr. Judson Daland, of 

 Philadelphia, has invented an instrument for counting- 

 blood-corpuscles, which works on the centrifugal-force 

 principle, and accomplishes the measurement by means of 

 comparative bulks. A quantity of blood is placed in a 

 finely graduated tube and the latter revolved at a speed of 



