CHEMISTRY OF THE PROTOPLAST 69 



when phloroglucin or tannin is present. Thus in capillary tubes, or artificial cells 

 formed by precipitation membranes ^of tannic acid and gelatine, treatment with 

 caffein, ammonium carbonate, &c., produces similar granular precipitates, which 

 have the power of reducing a silver solution. (Sees. 16 and 22.) Hence it is im- 

 possible to agree with Loew and Bokorny in their assumption that the precipitate 

 always and necessarily results from a polymerization of ' active albumin.' 



For a science dependent on facts, and not on dogma, the speculations of 

 L. and B. cannot be regarded as forming even a tenable temporary working hypo- 

 thesis. Indeed, it is hardly possible that vital activity could be the inalienable 

 property of a single chemical substance, or that all the phenomena of life could 

 result from the changes which a single chemical substance undergoes. 



The above objections and criticisms apply only to the incorrect interpretations 

 and conclusions drawn by Loew and Bokorny from the facts observed by them. 

 That particular proteid substances play an important part in the vital mechanism, 

 and that various changes may occur in them at death, are general conclusions 

 attained long ago. Independently of Loew and Bokorny's -speculative hypothesis, 

 it has been concluded on other grounds that a continual decomposition of proteid 

 substances is necessary for the maintenance of active life, and that some form of 

 albumin or albumin-compound may continually be produced, the instability of 

 which is the direct cause of the phenomenon of respiration, and of other vital 

 processes as well. (Chaps. VIII and IX.) It is possible that among such physio- 

 logically active substances aldehyde groups may play a part, and perhaps many 

 forms of sugar also, for carbohydrates may be combined with and form a con- 

 stitutional part of the molecule of certain proteid substances, e. g. glucosides, such 

 as mucin. 



