. A text-book of human physiology . FiG. 22.—A white blood corpuscle of the frog, contaniing an anthrax bacillus. The two figureswere drawn from the same cell at different times, after Metschnikoff. logical causes, the dfliris is taken up In the leucocytes and is removed. Theleucocytes play an imjmrtant role also in disposing of the pathogenic Bacteriawhich find their way into the body, since they are aide to eat and to digestsuch organisms (Fig. 22), and thereby to afford the body substantial pro-tection against infection (Metschnikoff). The more highly organized elementary organisms provided
. A text-book of human physiology . FiG. 22.—A white blood corpuscle of the frog, contaniing an anthrax bacillus. The two figureswere drawn from the same cell at different times, after Metschnikoff. logical causes, the dfliris is taken up In the leucocytes and is removed. Theleucocytes play an imjmrtant role also in disposing of the pathogenic Bacteriawhich find their way into the body, since they are aide to eat and to digestsuch organisms (Fig. 22), and thereby to afford the body substantial pro-tection against infection (Metschnikoff). The more highly organized elementary organisms provided with cilia anda cell mouth, such as the ciliate Infusoria (Figs. 24 and 28), ingest solid. Fig. 23.—VampyrcUa spirmjrircc, a rhizopodous unicellular organism, ingesting the contents of an alga cell, after Cienkowski. particles liy creating with their cilia a vortex so directed that the particlesare driven into the mouth. In this and other similar ways of taking up solidparticles the organism can exercise an actual choice of nourishment; certainKhixopoda for example eat only certain alga cells (cf. Fig. 23). 38 THE CELL C. DIGESTION J Tlie solids taken up in this way by tlic cells must unders^o various change.^in order that they may be of use to the cell. Oltcii this is true also withthe dissolved foods. All such processes l)y which the foods arc chanj^ed sothat they may be assimilated or further elal)oratcd by the cell are includedunder the term digedion. The digestion accomplished by the cell is either extra- or the former case digestion takes place under the influeuce of special sub-stances, the enzymes, formed by the cell. These substances, like cataly
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