382 



COLLOIDS IN BIOLOGY AND MEDICINE 



Aluminium is the bond between the earth alkalis and the heavy 

 metals. It coagulates albumin in " irregular series " and under certain 

 conditions the albumin-aluminium precipitates are reversible. In 

 this connection, thallium coagulates the protoplasm of aquatic plants 

 (spirogyra, elodea, etc.), but they recover when replaced in their 

 original medium (J. Szucs). 



The soluble salts of heavy metals form irreversible metal albumin 

 precipitates with albumin which either flock out immediately or, 

 depending on the concentration of the salt solution, persist in the 

 colloidal condition. 



For this property of the salts of the heavy metals, besides the 

 valence, the electrolytic solution pressure (see H. BECHHOLD **) is 

 determinative; colloid precipitation depends upon these two factors. 

 The toxicity threshold of the various salts of the heavy metals 

 has been arranged in series. MATHEWS* tested it on the motor 

 nerves of frogs. KAHLENBERG and TRUE, as well as F. D. HEALD, 

 tested them on plant seedlings. I reproduce (from R. HOBER) the 

 series determined by MATHEWS for the inhibition of the develop- 

 ment of the fertilized eggs of the sea anemone, fundulus heteroclitus. 



The exceptions which ZnCl 2 and CdCl 2 show (according to R. 

 HOBER) may depend in the first instance upon strong hydrolysis 

 (acid reaction) and in the latter on the smaller amount of electro- 

 lytic dissociation together with greater lipoid solubility. 



For the antagonistic action of ions of the heavy metals see pages 

 70 and 378. 



The intravenous injection of the salts of the heavy metals, which 

 is associated with precipitation of protein, causes in suitable doses 

 anaphylactic phenomena which may be explained by what has been 

 said on page 210. 



The salts of the heavy metals in respect to their toxicity appear 

 to me to have powerful specific influences. For instance, copper 



