130 ANATOMICAL TECHNOLOGT. 



Place a small compressor on the artery just centrad of the point 

 of injection, and withdraw the canula. At least two hours should 

 elapse before dissection is begun or an injection made with plaster 

 or gelatin. In the interval the hair may be clipped (see Chap. VI.). 

 After clipping, if no other injection is to be made, the animal may 

 be placed in alcohol, 42-55 per cent. 



§ 285. If only the cephalic half of the body is to be preserved, 

 not more than one liter of alcohol may be needed, and the operation 

 of abdominal transection should be carried as far as to open the 

 abdomen and puncture the diaphragm (§ 238). 



Then, in place of removing the viscera at once, proceed as fol- 

 lows : — 



Grasp the rectum as far caudad as possible, and force its con- 

 tents cephalad. Place two ligatures on it (Fig. 41), about one cm. 

 apart, and cut between them. 



With the scissors and tracer divide the mesentery of the large 

 intestine and that of the small intestine, to a point opposite the 

 cephalic end of the left kidney (Fig. 101, ren). 



Pass a strong thread from this point around the stomach and 

 liver, 1-2 cm. from the diaphragm, and tie it very firmly. The lig- 

 ature should cut deeply into the substance of the liver. 



With the tracer expose the aorta opposite the caudal end of the left 

 kidney. Open the aorta as directed (Chap. IV.) for the A.femoralis. 

 Inject alcohol as directed (§ 284) ; then inject alcohol into the lungs 

 as directed in § 281. Remove the abdominal viscera by an incision 

 1-2 cm. caudad of the ligature, taking care not to displace the latter. 



§ 286. Treatment of Special Organs and Tissues. — The blood 

 should be washed off with water or weak brine. Very vascular 

 parts, like the liver or spleen, should be gently manipulated so as 

 to expel most of the blood. 



In respect to the strength of alcohol required, the soft parts 

 form three groups, as follows : — 



Brains, embryos, the liver, spleen, the glands, and most inver- 

 tebrates should be laid upon cotton in natural attitxides, first in 

 alcohol of 52-67 per cent. ; after two days in 95 per cent., for a 

 week ; lastly, for exhibition or storage, in 75-95 per cent. 



Muscular organs, including the heart and alimentary canal, 

 may be hardened and permanently preserved in 42-55 per cent. 

 The same strength is adapted to most entire animals. 



