HOW TlIK AN'lMAl. LIVKS 235 



more difficult to kill tlian tho organism is wlieii iu un actively 

 S^ovi'iiig condition. 



390(1. A precipitate, in chemistry, is a more or less solitl 

 luntorial, which is tho result of chemical action, and which settles 

 to the bottom of the liquid in which it is formed. Thus, let the 

 pupil blow thi'ou^-h n straw into a bottle of lime water. The 

 liquid will become cloudy, and after u time the sediment will 

 »et.tle to the bottom. Tho pupil has added the carbon dioxid 

 (CO.) of his breath to the lime water, and carbonate of lime 

 (or limestone) has been formed. Compare 194<J. 



'.\9'2a. The action of the gastric juice may lie familiarly seen 

 in the curdliiig of milk in the cheese factory by means of 

 rennet. A little mince-meat mi.\ed with the scrapinjjs of the 

 lining membrane of a pig's stomach, rendered slightly acid 

 by n drep or two of muriatic acid and kept near blood-heat 

 (IMJ°F), will soon be completely dissolved, with the formation 

 of peptone. 



39'J/>. Rennet is the digestive principle derived from the 

 fourth stomach of ruminants ((), Fig. 87 1. This stomach is 

 taken from calves and dried ; and the stomach itself is then 

 spoken of as rennet. The stomach of adult animals could also 

 bo use<l, if necessary. 



393a. The gastric apparatus of a chicken is shown in Fig. 

 8S. The crop is at a, the proventriculus at b, and the gizzard 

 at r 



•i'Jiki. An emulsion is that condition in which fatty or 

 oily materials are so intimately mixed with the liquid in which 

 they nro placed that they act much as if they were in actual 

 solution, even passing through membranes. Most farmers are 

 now familiar with the u. -..-..,.. emulsion, used as an insecti- 

 cide i'iiHio). 



399rt. Glycerin in ii ^■<lI..rll•s^ liquid which is aHsm-iated with 

 fats or fat -acids, ond which may be derived tnnu them. Its 

 coiiijH.Hition ia Call:. <>FI 3. It is ofti n made from tho fats by 

 urtiti. ml means, and is used in medicine and the arts. Also 

 spelled glycerine. 



4ftCi. Two villi are shown in Fig. M>. The singular form of 

 the wurd la vuiua. 



