152 (;BNERAL physiology 



the blood outside the blood-vessels, and the beaker be warmed in 

 a digestion-chamber to the body-temperature, it is found after 

 some time that the solid flake of fibrin begins to swell, to become 

 transparent upon the outside, and gradually to become dissolved 

 in the liquid. Finally, the whole flake, as such, disappears, and in 

 its place there is found dissolved in the liquid ^je^Ji^owe, that modi- 

 fication of proteid which, as has already been seen, arises by a 

 hydrolytic cleavage of the polymeric proteid molecule, is soluble in 

 water, and diffuses through organic membranes. Besides the 

 peptone there are found also certain transition-stages between the 

 native albumin and the peptone, which are likewise soluble in 

 water and are termed albumoses. We shall presently discuss more 

 in detail the peculiar manner of working of the ferments. 



That which happens, in extraceHular digestion, outside the cell- 

 body, and which can be imitated even in the test-tube, takes place 

 in intracellular digestion within the protoplasm. Likewise here 

 the process can be followed best in the naked protoplasmic body 

 of Ehizojwda. Lieberkuhnia is a large fresh-water rhizopod, from 

 the egg-shaped, membranous shell of which thick, branching 

 pseudopodial filaments jarotrude through an opening at the pointed 

 pole (Fig. 50). When the Lieherkuhnia seizes and digests ^ an 

 infusorian that carelessly swims against its pseudopodia, it can 

 be seen with the microscope that the prey first becomes attached 

 to the pseudopodia, entangles itself more and more firmly by 

 its strong efforts to escape, and gradually becomes surrounded 

 either wholly or partially by the pseudopodial protoplasm (Fig. 51). 

 For some time the movements of the infusorian continue ; then 

 they become feebler, and at the same time its body-form begins 

 to change. It decreases in size constantly, while the liquid 

 and gTanular parts of its protojalasmic body pass over into the 

 pseudopodial protoplasm, mix with it, and are no longer seen to 

 stream to the central body of the Lieberhulmia. Thus, gradually, 

 the whole body of the infusorian becomes dissolved and its liquefied 

 contents mix with the protoplasm of its captor, until none of it is 

 longer distinguishable. In other cases of intracellular digestion 

 the food-body, e.g., in Amceba and Infusoria, becomes surrounded 

 by a food-vacuole within the endoplasm, and is dissolved in the 

 same manner as in the exoplasm of the Licherkiilinia. Further, 

 the observations that have been made upon the Infusoria by Green- 

 wood ('94) are very interesting. She followed the fate of the in- 

 gested food-masses in the Vorticellina-, especially in Carchcsium 

 (Fig. 52), and found that, while they are undergoing digestion, 

 they take a perfectly definite path within the cell-body — viz., 

 from the cell-pharynx {Gf. Vorticdla, p. 146, Fig. 46) to the bottom 

 of the cell and back to the mouth-opening, where the undigested 

 masses iirt; cast out. It is very noteworthy that the food-masses 

 ' Cf. Verwom ('81), 1). 



