8 MANUAL OF ZOOLOGY. 



composed of this living basis, but all contain a greater or 

 smaller amount of other materials, which are in one sense 

 dead. The real phenomena of vitality are conditioned, there- 

 fore, by certain special portions of the organism, which are 

 alone formed of this living matter ; and this matter in chemical 

 composition and physical characters appears to be identical in 

 all living beings whether animal or vegetable. To this physical 

 basis the names of " protoplasm " or "bioplasm" are applied. 

 The lowest organisms consist of little else but simple unmodi- 

 fied protoplasm ; but even in the most complex organisms it 

 can be shown that their essential parts, in which alone vitality 

 is inherent, are similarly composed of protoplasmic matter. 



As regards its nature, protoplasm, though capable of forming 

 the most complex structures, does not necessarily exhibit any- 

 thing which can be looked upon as organisation, or differentia- 

 tion into distinct parts ; and its chemical composition is the 

 only constant which can be approximately stated. It consists, 

 namely, in all its forms, of the four elements, carbon, hydrogen, 

 oxygen, and nitrogen, united into a proximate compound to 

 which Mulder applied the name of " proteine," and which is 

 very nearly identical with albumen or white-of-egg. It further 

 appears probable that all forms of protoplasm can be made to 

 contract by means of electricity, and " are liable to undergo 

 that peculiar coagulation at a temperature of 4o-5o centigrade, 

 which has been called ' heat-stiffening ' " (Huxley). As viewed 

 under the microscope, protoplasm presents itself as a clear 

 viscous, semi-fluid substance, which is commonly rendered 

 granular by the presence of disseminated particles of fatty 

 matter, and which is deeply stained by immersion in a solu- 

 tion of carmine. 



In addition to the physical and chemical properties of proto- 

 plasm, many writers are in the habit of speaking of the " vital 

 properties " of this substance. These so-called " vital proper- 

 ties " are necessarily the same as those manifested by living 

 beings in general, and consist in the power exhibited by living 

 protoplasm of assimilating foreign matter, of reproducing itself 

 by the detachment of portions of its substance, and of having 

 certain relations with the world outside itself. As regards the 

 last of these points, protoplasm, in its living state, when uncon- 

 fined by any rigid wall or outer envelope, possesses the power 

 of throwing out longer or shorter prolongations or processes 

 of its own substance (" pseudopodia "), by means of which it 

 can obtain food, or, if free, move about. Even in vegetable 

 cells, where a rigid cell-wall is as a rule present, the protoplasm 



