REVIEWS 141 



of the normal volume of the blood. On the other hand, we find such things 

 as the electrical charge of particles, their oxidising and reducing properties 

 indicated as of great importance, although there is at present no satis- 

 factory evidence that this is the case. 



It is remarkable that the author appears to be so obsessed with the 

 importance of the colloidal state in itself that he overlooks one unquestion- 

 able characteristic of matter in this state, which makes the use of powerful 

 drugs like arsenic, iodine, etc. in colloidal solution of value. This is the 

 comparative slowness of reaction, due to action from the surface only. Thus 

 a small effect may be produced, although exerted for a prolonged time. The 

 fact suggests that what is really active is the very small amount of sub- 

 stance in true solution gradually dissolved by the tissue fluids from the 

 colloidal particles. A more exact account of the work of the late Henry 

 Crookes would have been welcome, especially as the toxic properties of 

 metals were described by Naegeli in 1893. If it were true, as stated on 

 p. 75, that colloidal metal sols are rapidly fatal to bacterial parasites with- 

 out any action on the host, an immense advance in therapeutics would have 

 been made. The author can scarcely expect the colloidal state to be re- 

 garded as the ideal one for administration of alkaloids (p. 105) in view of 

 Dale's work on cocaine, of which he appears to be unaware. Mr. Searle 

 propounds the view that a drug must be converted into the colloidal state 

 before it is efhcient, and makes the extraordinary statement that this hap- 

 pens more rapidly by intramuscular than by intravenous injection. More- 

 over, in this connection, although it is undoubtedly true that all cellular 

 reactions occur in heterogeneous systems, it must not be forgotten that 

 the most powerful actions are exerted on these systems by electrolytes and 

 other substances in true solution. 



There are some minor slips which might be corrected in a future edition, 

 such as the attribution to Tyndall of Faraday's discovery of the scattering 

 of light by suspended particles in colloidal solution. 



The work on the whole contains much that is of interest, but would 

 be greatly improved by a more critical treatment of the evidence of alleged 

 physiological actions, and especially of the clinical cases, most of which 

 have no value as evidence. It is to be feared that the author accepted 

 without question what he was told. -^y^ -^i ^ 



Laboratory Manual of Elementary Colloid Chemistry. By Emil Hatschek. 

 [Pp. viii + 135, with 20 illustrations.] (London : J. and A. Churchill, 

 1920. Price 65. 6d. net.) 



The appearance of this little book is significant. It shows that colloid 

 chemistry has at last arrived at that stage in its development in which it is 

 no longer regarded as an exceedingly specialised branch of chemistry, but is 

 in fact to be included in the normal advanced chemical curriculum. The 

 manual is admirably adapted to the purpose which its writer has had in 

 view, namely, " to supply accurate and very detailed directions for carrying 

 out the fundamental operations " of colloid chemistry. 



Since the book is the first of its kind, and has been written by one who 

 is himself an authority on the subject, it may be well to indicate its general 

 scope by enumerating the subjects dealt with. These are : Dialysis, ultra- 

 filtration, optical examination, suspensoid sols and suspensions, emulsoid 

 sols and gels, emulsions, cataphoresis, coagulation, protection, viscosity, 

 adsorption, capillary analysis, and the Liesegang phenomenon. 



In general only laboratory glass apparatus is required, stress being 

 rightly laid on the necessity of employing resistance glass. The greater 

 part of the course can therefore be given with ordinary laboratory equip- 



