INTRODUCTION 43 



become clouded in a mist of speculation. Other theories, such as 

 the reticular and fibrillar theories, associated with the names of 

 Heitzmann, Schafer, Flemming, etc., are based upon the actual 

 pictures of different types of protoplasm. 



The larger vacuoles in different t\i)es of Protozoa to which the 

 names cavulse and contractile vacuoles are given, are interpreted 

 according to the alveolar theory as due to the flowing together and 

 fusion of adjacent alveoli. This is certainly the case in the forma- 

 tion of a contractile vacuole of Amoeba proteus where the beginnings 

 of a vacuole may be watched under the microscope and the coales- 

 cence of minute vesicles noted. In a sunilar way the relatively 

 hugh cavulse or pseudo-alveolse characteristic of Actinosyhoerium 

 eichhornii and of Radiolaria may be accounted for. 



Physically, protoplasm is to be compared with an emulsion of 

 colloidal substances which, as Lord Rayleigh and others have 

 pointed out, can as a polyphasic system, retain the emulsoid condi- 

 tion only as long as the limiting membranes between dispersed and 

 dispersing media are intact. In the activities of a living, moving 

 cell, there must be a continual disturbance of this physical equi- 

 librium and a constantly changing configuration of the protoplasm 

 due to the manifold chemical actions which are characteristic of 

 living matter. 



Chemically, protoplasm is not a substance but a harmoniously 

 working aggregate of dift'erent interacting substances which have 

 been identified in general as nucleins, nucleo-albumins, nucleo-pro- 

 teins, carbohydrates, fats, salts, and the almost endless variety of 

 derivatives from these and from their combinations. With the 

 exception of the Mycetozoa which have been used extensively for the 

 purpose of protoplasmic analysis, protozoan protoplasm owing to the 

 minute size of the individuals, has been very little studied in connec- 

 tion with the chemistry of protoplasm, and our present knowledge 

 concerning it is based mainly on morphological considerations 

 together with the results of chemical analysis of protoplasm in higher 

 t;y'pes of animals and plants. 



The granules which invariably appear in protoplasm, and which 

 are probably intimately connected with the varied activities going 

 on during life are different in their chemical make-up although, 

 morphologically, they appear much the same. This is shown by 

 their reactions to micro-chemical tests of different kinds and it is 

 not unreasonable to infer that the specificity of protoplasm in dif- 

 ferent species of Protozoa is due in large part to the chemical and 

 physical composition of these granules and interactions going on 

 amongst them. 



As Mathews points out, the essential differences in chemical 

 actions in protoplasm and in physical nature are: (1) The order- 

 liness with which they are carried on; (2) the speed of the reactions. 



