THE EC0N02IICS OF ALCOHOL. 117 



§ 275. The Economics of Alcohol. — In the economical employ- 

 ment of alcohol, four matters are to be considered : (1) The use of 

 different grades for appropriate purposes ; (2) The prevention of 

 evaporation ; (3) The avoidance of leakage ; (4) The improvement 

 of "old" (deteriorated) alcohol. 



§ 276. The Use of Appropriate Grades. — Upon zoological specimens alcohol is em- 

 ployed for three distinct purposes : preparation ; storage ; exhibition. Different degrees 

 of clearness and strength are needed for these different purposes, and the safety of speci- 

 mens, economy, and the appearance of collections depend upon the use of each grade for 

 its appropriate purpose. For example, the commercial (95 per ceut.) alcohol is just strong 

 enough for some purposes, much too strong for others, and needlessly clear and pure for 

 others. 



The following remarks apply to all vertebrates, and the more general ones to most 

 invertebrates also. Among the invertebrates the jelly-fishes and some other soft forma 

 cannot be satisfactorily preserved by means of alcohol, and most of the rest should be 

 treated like the brains and embryos of vertebrates. 



§ 277. Strong alcohol coagulates the tissues so as to form a firm 

 ectal layer, through which it afterward passes with difficulty. 

 With a small specimen, the only objection may he the corrugation 

 and distortion of the specimen. But with a large and fleshy one, 

 the outside may harden while the interior is actually decomposing. 



There is no difficulty in preserving the skeletal muscles and 

 the limbs, but the brain and abdominal viscera, especially the liver, 

 are not only more prone to decomposition than the muscles, but 

 naturally excluded by them from the alcohol. Unless, therefore, 

 definite measures are taken prior to immersion (§ 286), some of the 

 viscera wiU surely fail to be preserved. These measures will vary 

 according to the size of the specimen and the use to be made of 

 it, and, under some circumstances, the opportunity for using the 

 required instruments. 



§ 278. The four accessory measures are named in the order of 

 their simplicity : (1) Freely opening the abdomen ; (2) Injecting 

 alcohol into the thorax and abdomen ; (3) Injection of alcohol into 

 the large hollow viscera ; (4) Injection of alcohol into the arteries. 



§ 279. As a preliminary to any of them, the animal should be 

 bled, if practicable, -jv^hile under the influence of an anaesthetic. As 

 soon as the cat is quite asleep, the femoral vessels may be exposed 

 as directed for coarse injections (Fig. 39). and the V. femoralis 

 divided. When the venous flow slackens, the artery may be opened. 

 In this way most of the blood in the larger vessels is removed, and 

 preservation is facilitated. 



