IDEAL TYPE OF A CELL. 9 



and animals and the fertilised ovum occupy an unique and 

 isolated position which is not assumed by any other being in 

 the whole scale of creation, we must exclude the nucleus as an 

 unnecessary factor in the ideal type of an elementary organism. 

 We must also in future apply the histological term cell to the 

 morphological elements of the higher animals or to independent 

 living organisms, even if we are unable to discover anything 

 more in their structure than that they are little masses of 

 animal sarcode or protoplasm. Nor will any essential change 

 be made in our views even if it be hereafter proved that there 

 are cases where the nucleus is not only present but plays an 

 extraordinarily important role. 



I* have shown that little masses of protoplasm, destitute of 

 nuclei, and which might be presumed to be the remains of cells, 

 may still present some of the phenomena of life. I also now 

 know that in other places where many young cells are collected 

 together, fragments or minute separated particles occur about 

 the size of a nucleolus, which, if they become attached to the 

 slide, sometimes exhibit very lively movements, and this espe- 

 cially if the object plate be warmed to from 68 to 70 Fahr. 



May we now, in consequence of our new definition, consider 

 these little masses as cells ? and shall we be justified in giving 

 this name to all the minute particles which, when armed with 

 instruments of still greater penetration, we may be able to per- 

 ceive and find capable of spontaneous movements ? In the 

 present state of our knowledge we shall certainly reply in the 

 negative. We shall continue to regard such minute masses as 

 living or organised matter without reference to their size, so 

 long as the optical means of research at our disposal do not i 

 permit us to make the observations necessary for a different 

 statement. 



We cannot, however, term these masses cells, any more than 

 we can apply the name of the whole animal to the excised 

 heart of a tortoise. In order that we should apply the term 

 " cell " to such an isolated fragment of living substance, it is 

 necessary that we should recognise the whole group of phe- 



* Uber contractile Korper in der Milch, " On the cjntractile bodies in 

 Milk," Wiener Sitzungsberichte, 1866. 





