740 SUMMARY OF CURRENT RESEARCHES RELATING TO 



not SO treated. If the collodion has been too much thinned with 

 ether the fact will become apparent from the softening of the paraffin, 

 and may be remedied by waiting for the evaporation of the ether or 

 by adding thicker collodion. 



This process can in no way be considered as a substitute for the 

 ordinary method of cutting objects, since it requires more time and 

 closer attention to details, but for those cases where there is a 

 liability to crumbling, or where sections of sufficient thinness cannot 

 be procured free from folds, it will doubtless be found very service- 

 able." 



Sections in Series.* — Herr F. Spec remarks that the success of 

 cutting sections depends on the quality of the imbedding mass, on the 

 shape which is given to the paraffin around the object to be cut, and 

 on proper manipulation in cutting. His imbedding mass consists of 

 paraffin with a melting-point of 50" C, which is prepared by melting 

 it in an open porcelain dish over a spirit-lamp flame, and further 

 heating it until it assumes the colour of yellow wax or honey. When 

 cool, it appears as a homogeneous mass without air-bubbles ; its cut 

 surface feels soapy and greasy. This material has the advantage that 

 sections made with a microtome adhere firmly together by their edges 

 at the ordinary temperature of the room. 



To imbed specimens, they are placed in the mass at a temperature 

 of 60°-65° C. for 4-6 hours till they are thoroughly permeated by 

 the paraffin, which is then allowed to cool. To cut sections, the 

 superfluous paraffin is cut away and the remaining piece of paraffin so 

 arranged that the edges of the sections which are made pass over each 

 other and adhere together. This end is attained by giving the 

 paraffin the shape of a parallel sided prism, of which the base is a 

 right angle. The paraffin is melted on to a cork by a hot spatula, 

 and fastened on to the object-carrier of the microtome in such a way 

 that its broad side is parallel to the edge of the razor. As a rule, a 

 layer of paraffin about 1/2-1^ mm. thick should be left round the 

 specimen. No section should be thicker than 1/100 mm., and all the 

 sections should be as nearly as possible of equal thickness. If thicker 

 than 1/100 mm. they roll easily, while too great unevenness inter- 

 feres with the continuity of the ribbon. The best ribbons are ob- 

 tained with specimens which have a small surface. For practical pur- 

 poses the ribbons should not be longer than 15-20 cm. To fix them on 

 the slide the author uses the gum solution of Tlogel with good results. 



New Carmine Solution.f — For the investigation of Protozoa, 

 Medusae, Echinodermata, Lumhrici, Podura, &c., Dr. 0. Hamann uses 

 a solution which is made as follows : — 30 grms. carmine are mixed 

 with 200 grms. concentrated ammonia, and glacial acetic acid is 

 added until the solution is neutral or only faintly acid. The filtered 

 solution is ready for use in two to four weeks. Dr. W. Krause recom- 

 mends it, used warm, for staining the retina, nervous system, and 

 glands of Vertebrata. 



* Zeitschr. f. Wiss. Mikr., ii. (1885) pp. 6-12. 



t Interaat. Monatsschr. f. Auat. u. Histol., i. (1884) Heft 5. 



