MBMOVAL OF TBE BRAIN. 423 



The cephalic end of the dlacoelia is decidedly narrowed, and tba 

 walls are thin. 



§ 1098. Remove the basis cranii so as to expose the basis en- 

 cepTiali as far as the aula. Observe the sub-cordate hypophysis 

 underlying the mesencephalon, but attached by its base to the 

 slight intumescence — the tuber cinereum— forming the floor of the 

 diencephalon. 



In case more tlian one brain is examined, the second shoidd be transected with a 

 very sharp scalpel, and drawings made to show the form of the coelise at different 

 points. A third brain may be divided upon the meson, and a fourth opened from the 

 ventral side. With all of these the metatela should be left in place. Still others may be 

 prepared to show special points. When many brains are available, each should be devoted 

 to a given section or dissection, all other parts being untouched, so that the special fea- 

 tures may be more easily recognized. 



REMOVAL OF THE BRAIN OP THE CAT. 



§ 1099. The method first described is to be preferred when the 

 brain is wanted entire, and especially when the length of the nerve 

 roots is an object ; see Wilder, 11. 



Instruments and Materials. — Medium scalpel , Charrifere scalpel ; arthrotome ; tracer ; 

 curved scissors ; bone scissors ; forceps ; nippers, medium or large and small ; large tray 

 for the cat ; small tray, or a folded cloth, for the head ; block ; small towel, or piece of 

 muslin, for aiding the grasp of the head ; waste paper ; basin and towel ; dish of 7 per 

 cent, brine, about 6 cm. deep and 20 wide. cont£tining some well soalsed cotton ; bowl of 

 normal salt solution (15 grams of salt to 2000 cc. of water), sufEcient to cover the head 

 after its separation from the body) ; bowl for catching the blood ; glass box (§ 307) ; wide 

 mouthed jar or covered dish of 62-67 per cent, alcohol, with some well soalied cotton at the 

 bottom ; a cat's skull ; figure of the bcms cranii (Fig. 57) ; figure of the iasis encephaii 

 (Fig. 115, PI. II, Fig. 'Sfr^able of the cranial foramina (g 562). 



§ 1100. Killing the Cat. — The cat may be drowned, but is more conveniently anaes- 

 thetized (§ 193). Kill the fleas as directed in § 193. As soon as respiration ceases, sus- 

 pend it by the head over a pail or the sink, and expose and divide the femoral artery and 

 'cein (Fig. 39) centrad of the valves in the vein (§ 362) ; even if little blood escapes, the 

 amount in the brain will be reduced. If it be desired to ascertain the weight of the entire 

 animal, the blood should be caught in the bowl and weighed. 



For injection with alcohol, see §§ 284, 285. 



For injection of the plexuses, see § 1136. 



If the more delicate internal parts or the microscopic structure are to be studied, the 

 remaining operations for the procurement of the brain should be performed within 24 

 hours. But if the specimen is desired only for the fissures or tlie coarser anatomy, re- 

 moval may be deferred for a week, provided the head be kept in a cool place. It should 

 not, however, be allowed to freeze. 



§ 1101. Decapitation. — From the dextral angle of the mouth di- 

 vide the skin along a line extending nearly caudad for 6-8 cm. If 



