THE DISTINCTIVE CHARACTERS OF ANIMALS. 45 



The great majority of the higher plants, on the contrary, 

 are able to manufacture protein when supplied with carbonic 

 acid, ammoniacal salts, water, and sundry mineral phosphates 

 and sulphates, obtaining the carbon which they require by 

 the decomposition of the carbonic acid, the oxygen of which 

 is disengaged. One essential factor in the performance of 

 this remarkable chemical process is the chlorophyll which 

 these plants contain, and another is the sun's light. 



Certain animals {Infusoria, Ccelenterata, Turoellaria) 

 possess chlorophyll, but there is no evidence to show what 

 part it plays in their economy. Some of the higher plants 

 when parasitic, and a great group of the lower plants, the 

 Fungi (which may be parasitic or not), are, however, devoid 

 of chlorophyll, and are consequently totally unable to derive 

 the carbon which they need from carbonic acid. Nevertheless 

 they are sharply distinguished from animals, inasmuch as they 

 are still, for the most part, manufacturers of protein. Thus 

 such a Fungus as Penicillium is able to fabricate all the con- 

 stituents of its body out of ammonium tartrate, sulphate, and 

 phosphate, dissolved in water {see supra, p. 14, note) ; and 

 the yeast-plant nourishes and multiplies with exceeding rapid- 

 ity in water containing sugar, ammonium tartrate, potassium 

 phosphate, calcium phosphate, and magnesium sulphate. 



Nevertheless, the experiments of Mayer have shown that 

 when peptones are substituted for the ammonium tartrate, 

 the nutrition of the yeast-plant is favored instead of being 

 impeded. So that it would seem that the yeast-plant is able 

 to take in protein compounds and assimilate them, as if it 

 were an animal ; and there can be no reasonable doubt that 

 many parasitic Fungi, such as the JBotrytis Bassiana of the 

 silk-worm caterpillar, the JEmpusa of the house-fly, and, very 

 probably, the Peronospora of the potato-plant, directly as- 

 similate the protein substances contained in the bodies of the 

 plants and animals which they infest ; nor is it clear that 

 these Fungi are able to maintain themselves upon less fully 

 elaborated nutriment. 



Cellulose, amyloid, and saccharine compounds were former- 

 ly supposed to be characteristically vegetable products ; but 

 cellulose is found in the tests of Ascidians ; and amyloid and 

 saccharine matters are of very wide, if not universal, occur- 

 rence in animals. 



And on taking a comprehensive survey of the whole ani- 

 mal and vegetable worlds, the test of locomotion breaks down 

 as completely as does that of nutrition. For it is the rule 



