THE ZINC CHLORID PROCESS. 435 



Turn the cephalic end upward, and very carefully dislodge the 

 Lobus olfactorius. When this is done, the cephalic end of the 

 hemisphere will be easily freed from the dura. Hold the skull with 

 its venter down over the normal salt solution, and let the brain roll 

 into it. 



1122. Hardening. For a few hours the hemiencephala should 

 rest upon their mesa ; then a little bed of absorbent cotton should 

 be made for each, so that it may rest with the meson uppermost 

 and yet not be distorted. 



After two days transfer to 95 per cent, alcohol, changing the 

 position as above. 



1123. The Zinc Chlorid Process. The preservation of brains by means of a solution 

 of chlorid of zinc is mentioned or more or less fully described by Gratiolet (A, II), Bischoff 

 (12, 11), Giacotnini (1 [abstract in Jour, of Anat. and Pbys., XIII]), Rolleston (1) and 

 Osier (1, 2). 



Oar own experience is not yet sufficiently extensive to enable us to form an opinion 

 respecting its merits, and we here give (slightly modified verbally) the condensed direc- 

 tions which accompanied the admirable preparations of the human brain exhibited by 

 Osier at the meeting of the Am. Assoc. Adv. Sci., 1879, and substantially reproduced in 

 his second paper (2). 



" (1) Immerse in a zinc chlorid [saturated] solution (' Burnett's ' will answer). Turn 

 two or three times a day. On the second day remove the pia. Let it remain until it no 

 longer sinks (8-10 days). 



" (2) Immerse in alcohol of commerce [95 per cent.] for 10-12 days, turning often to 

 prevent distortion. 



" (3) Immerse in good glycerin to which has been added 4 per cent, of carbolic acid. 

 Let it remain until it sinks to the level of the liquid. 



" (4) Set aside for several days until the surface is dry. Then cover with several layers 

 of gum-elastic varnish." 



1124. Injection of the Ccdiw. (A) With alcohol. When the coelise and plexuses are 

 to be studied, it is an advantage if the former have been first filled with strong alcohol. 

 This is most readily done after the entire brain has been placed in the weaker alcohol 

 ( 1105). 



Gently detach the hypophysis with the forceps, or leave it attached by a part of the 

 infundibulum. Then fill a small syringe with 95 per cent, alcohol, apply the outlet (with- 

 out a canula) to the Fm. infundibuli, and inject slowly until the LI. hypocampa (PI. II, 

 Fig. 3) is seen to swell slightly. Repeat the operation several times at intervals of 1-3 

 hours. 



1125. (B) With plaster. This is for the sake of obtaining a cast of some part of the 

 coelise. It is best done while the brain still rests in the calva ( 1103). See description of 

 Fig. 119. This method was employed by us before Welcker's method of injecting wax was 

 known to us (1 [abstract in Jour. Anat. and Phys., XIII, 283]). 



After the injection the brain should remain wholly undisturbed for at least half an hour. 

 The parts about the Fm. infundibuli, constituting the floor of the diaccelia, may then be 

 gently cut away with scissors so as not to break the cast. It is probable that a fracture 



