COLLODION AND OTIIKR IMI!KDDIN(J METHODS. 117 



and gradually saturated, first with benzol, and then with thin 

 and thick solution of benzol-balsam. It is then dried for a 

 day in the air and for several days more in a hot-air bath. 

 When hard it is ground in the usual way. 



180. WEIL'S Canada Balsam Method, see Zeit. wis*. Mik., v, 1888, 

 p. 200. 



181. GIESBRECHT'S Shellac Method. For hard parts only, spines 

 of Eihinus, shell, etc., see MorpU. Jahrb., vi, 1880, p. 95, or the abstract 

 in LEE uiid MAYER, Grundzilge. 



Congelation Masses. 



182. The Methods of Freezing. For the requisite manipula- 

 tions, and means of producing the requisite degree of cold, 

 see CARPENTER'S The Microscope (ether spray) ; JOHNE, Zeit. 

 wiss. Nik., xiv, 1807, p. 370 (liquid carbonic acid) ; WOLFF, 

 ibid., xxv, 1908, p. 175 (ethyl chloride) ; KUAUSE, ibid., 

 p. 289 (solid carbonic acid) ; JUNG, Verh. Ge.s. Naturf. Aertze, 

 Ixix, 1898, p. 129 (ethyl chloride); BRISSY, C. R. Soc. BioL, 

 Ixii, 1907, p. 1115 (liquid air). 



Fresh tissues may be, and are, frequently frozen without 

 being included in any mass. But the formation of ice 

 crystals frequently causes tearing of delicate elements, and 

 it is better to infiltrate the tissues with a mass that does not 

 crystallise in the freezing mixture, but becomes simply hard 

 and tough, such as one of those given below. 



When sections have been obtained, it is difficult to 

 manipulate them. OLT (Zeit. u-iss. Mile., xxiii, 1906, p. 327) 

 puts them into a 1 per cent, solution of gelatin, brings them 

 therein on to a slide, hardens for an hour in vapour of 

 formaldehyde, and soaks for a few minutes in formol of 10 

 per cent. ANITSCHKOW (ibid. } xxvii, 1910, p. 73) puts them 

 into alcohol of 50 per cent., gets them on to a slide prepared 

 with Mayer's albumin, presses down with paper, puts into 

 alcohol of 98 per cent., and thence through lower grades 

 into water. 



183. Gum and Syrup Masses. HAMILTON (Journ. of Anat. 

 and Phys., xii, 1878, p. 254) soaked tissues in syrup made 

 with double refined sugar, 2 ounces; water, 1 fluid ounce; 



