ADDRESS BEFORE THE BRITISH ASSOCIATION. 575 



of the jelly-like character of protoplasm, the idea for a time prevailed 

 that a structureless, dimly granular, jelly or slime destitute of organi- 

 zation, possessed great physiological activity, and was the medium 

 through which the phenomena of life were displayed. 



More accurate conceptions of the nature of the cell plasm soon be- 

 gan to be entertained. Briicke recognized that the body of the cell was 

 not simple, but had a complex organization. Flemming observed that 

 the cell plasm contained extremely delicate threads, which frequently 

 formed a network, the interspaces of which were occupied by a more 

 homogeneous substance. Where the threads crossed each other, granu- 

 lar particles (milkrosomen) were situated. Butschli considered that he 

 could recognize in the cell plasm a honeycomb-like appearance, as if it 

 consisted of excessively minute chambers in which a homogeneous more 

 or less fluid material was contained. The polar and spindle-like radia- 

 tions visible during the process of karyokinesis, which have already been 

 referred to, and the presence of the centrosome, possibly even dur- 

 ing the resting stage of the cell, furnished additional illustrations of 

 differentiation within the cell plasm. In many cells there appears also 

 to be a difference in the character of the cell plasm which immediately 

 surrounds the nucleus and that which lies at and near the periphery of 

 the cell. The peripheral part (ektoplasma) is more compact and gives 

 a definite outline to the cell, although not necessarily differentiating 

 into a cell membrane. The inner part (endoplasma) is softer and is 

 distinguished by a more distinct granular appearance and by contain- 

 ing the products specially formed in each particular kind of cell during 

 the nutritive process. 



By the researches of numerous investigators on the internal organi- 

 zation of cells in plants and animals, a large body of evidence has now 

 been accumulated, which shows that both the nucleus and the cell 

 plasm consist of something more than a homogeneous, more or less 

 viscid, slimy material. Recognizable objects in the form of granules, 

 threads, or fibers can be distinguished in each. The cell plasm and the 

 nucleus respectively are therefore not of the same constitution through- 

 out, but possess polymorphic characters, the study of which in health 

 and the changes produced by disease will for many years to come form 

 important matters for investigation. 



(To be concluded.) 



