544 THE POPULAR SCIENCE MONTHLY. 



Blood, upon leaving the vein, is separated into a liquid and a solid 

 part by librinogen, one of the proteids dissolved in it, undergoing a 

 change, by which it becomes insoluble fibrin ; muscular plasma, the 

 semi-solid constituent of muscular fiber, by solidifying after death, 

 and changing into fibrin, affords the well-known phenomenon of 

 rigor mortis. It is a process closely resembling these, by which 

 one of the soluble proteids of gluten, by accession of air and water, is 

 transformed into insoluble gluten fibrin. 



The conformity existing between the nitrogenous compounds of 

 vegetables and animals is not limited to the proteids mentioned, but 

 extends to various products of their decomposition. Diastase, the 

 fermentative agent originating from proteids in the seeds of many 

 plants during germination, is also present in the saliva of animals, 

 where it exerts upon amylaceous foods the same action of forming 

 sugar from starch. Agents very similar to pepsin, the digesting fer- 

 ment of the stomach, are to be found dissolved in the juices of various 

 plants ; upon contact Avith muscular fiber, or coagulated albumen, or 

 cheese, they Avill dissolve these bodies, and transform them into pep- 

 tones as well as pepsin does. Thus papayotin, a substance extracted 

 from the juice of Carica x>cipayn — a kind of fig-tree — is therapeutic- 

 ally applied for dissolving morbid membranes and tumors ; not less 

 are the well-known insect-devouring properties of the leaves of i\"e- 

 penthes, Drosera, and Utricularia, due to the presence of such ferments 

 in their viscid secretions. Leucin and tyrosin, amides occurring in 

 the roots of plants, which are both products of decomposition and 

 regenerators of albuminoids, are also found in animal organs. The 

 inflammation of skin, caused by touching a nettle, has been ascer- 

 tained to be due to a kind of decomposed, or changed, proteid ; and the 

 virulent properties of the secretions contained in the venom glands of 

 serpents having become known to depend on proteids, the conclusion 

 appears well founded that the virus of insects and other animals also 

 owes its pernicious effect to metamorphosed albuminoids, too, rather 

 than to formic acid, as had been hitherto believed. 



Many facts have been produced to show that, as the theory of evo- 

 lution supposes, there is a degree of consanguinity existing between 

 plants and animals : sexual differentiation, for instance, is common to 

 the higher forms of both of them. Sexes in both cases are sometimes 

 united in the same individual, sometimes separated. The lowest spe- 

 cies of both of them, consisting of single cells, propagate by simple 

 division. Scarcely a characteristic has been discovered in these living 

 cells of plasma, which might justify the making of a distinction be- 

 tween plants and animals. The voluntary movement ascribed to 

 the latter class is not plainly discernible in many cases, while many 

 low plants, such as diatomacem and certain bacteria are eminently 

 and continually engaged in lively motion, Ko striking difference is 

 to be observed in the sources of food and in the way in which it is 



