DR. DUFFIN, ON PROTOPLASM. 2061 
processes or bulgings that are formed. The phenomena 
described in the mucus-corpuscle and young epithelial cells 
closely resemble those observed in the pseudopodia of the 
Polythalamiz. The active movements of the molecules con- 
tained in the salivary corpuscles, the various shapes assumed 
by these corpuscles, either spontaneously or under the in- 
fluence of various reagents, and particularly the fact that 
magnetism is capable of arresting all this activity, have been 
fully described by Briicke.* The same author also describes 
the molecular movements of the white blood-corpuscles and 
of pus: “The granules which they extended evinced for a 
considerable time the same movements as the granules of the 
salivary corpuscles.” 
One very important question to which these observations 
gives rise relates to their bearing on the cell theory. It is 
evident that no proper membrane invests either the pseudo- 
podia of the Polythalamize, or the salivary or mucus-corpuscles. 
Briicke+ denies a membrane to the white blood-corpuscles 
and to pus, and has contested every argument that has been 
adduced in favour of its existence in the red blood disc. 
Beale takes the same view. Dr. Dalton has also contested 
the existence of this membrane. Brettauer and Stemacht 
have shown that membrane does not invest the whole of a 
particle of cylindrical epithelium, but only casts a conical 
mantle about the same. Dr. Beale$ has insisted upon the 
difficulties attending the acceptance of a proper membrane 
for the hepatic, renal, and other cells, and further states, that 
as in Guinea-pig’s blood, each single corpuscle becomes one 
tetrahedral crystal, it is impossible that there can be a proper 
membrane to the red blood disc. He also very truly re- 
marks that in young cells generally no cell-wall whatever 
exists; it is, therefore, impossible to regard the cell-wall as an 
essential structure. Thus grave doubts are thrown on the 
propriety of including the investing membrane in the defin1- 
tion of a cell. Schultze || does not hesitate to define the cell 
as a mass of protoplasm enclosing a nucleus, and he regards 
the formation of a chemically differentiated membrane on the 
surface as a retrogression. 
Beale has considerably extended this definition, and in- 
* “Die Elementar-organismen,” ‘ Kais. Akad. d. Wiss.,’ Bd. xliv, Oct., 
1861. 
+ Ibid. 
+ Bricke, ibid. 
§ ‘On the Structure and Growth of the Tissues,’ a Course of Lectures 
delivered at the Royal College of Physicians, 1861. 
| ** Ueber Muskelporperchen,” Reichert u. Du Bois Raymond’s ‘ Archiv,’ 
1861. i 
