12 THE CELL 



that, at first sight, they seem to have nothing in common, and 

 that hence it is impossible to compare them. For instance, if a 

 cell at the growing-point of a plant be taken and compared 

 with one filled with starch granules from the tuber of a potato, 

 or if the contents of an embryo cell from a germinal disc be com- 

 pared with those of a fat cell, or of one from the egg of an 

 Amphibian filled with yolk granules, the inexperienced observer 

 sees nothing but contrasts. Nevertheless, all these exceedingly 

 different cells are seen on closer examination to be similar in 

 one respect, i.e. in the possession of a very important, peculiar mix- 

 ture of substances, which is sometimes present in large quantities, 

 and sometimes only in traces, but which is never wholly absent 

 in any elementary organism. In this mixture of substances the 

 wonderful vital phenomena, which are dealt with later, may very 

 frequently be observed (contractility, irritability, etc.); and, more- 

 over, since in young cells, in lower organisms, and in the cells of 

 growing- points and germinal areas, it is in the cell-substance alone 

 (the nucleus of course being excepted) that these properties have 

 been observed, this substance has been recognised as the chief 

 supporter of the vital functions. It is the protoplasm or "forming 

 matter" of the English histologist, Beale (I. 3). 



a. Justification of the Use of the Term Protoplasm. 

 In order to know what protoplasm is, it is advisable to examine it 

 in those cells in which it is present in large quantities, and in 

 which it is as free as possible from admixture with other bodies ; 

 and amongst such the most suitable are those organisms from the 

 study of which the founders of the protoplasmic theory formed 

 their conception of the nature of this substance. Such organisms 

 are, young plant-cells, Amoebae, and the lymph corpuscles of 

 vertebrates. After the student has learnt to recognise the cha- 

 racteristic properties of protoplasm in such bodies, he will be able 

 to discover it in others, in which it is only present in small 

 quantities and is more or less concealed by other substances. 



It has been proposed (II. 10) to give up altogether the use of 

 the term protoplasm, since it has been associated with such 

 mistaken views ; for the word has now come to be used in so 

 indefinite and vague a manner, that it may be questioned whether 

 it is not at present more misleading than useful. 



However, this proposition cannot be considered to be advisable 

 or even justifiable in the present condition of affairs, for, although 

 it must be admitted that the word is frequently used incorrectly ; 



