January 3, 1901] 



NATURE 



227 



between them and the hexoses. The protones would, 

 according to this scheme, be considered as comparable 

 with the dextrins, and the protamines as comparable 

 with starch. It is true that our knowledge is still too 

 incomplete to enable us to carry the process still further, 

 so as to trace with accuracy the connection between the 

 protamines, on the one hand, and the proteoses and pep- 

 tones on the other ; but that need not prevent us from 

 considering the subject in the order above described, 

 especially since this arrangement has also the advantage 

 of passing from the simple to the more complex. A short 

 reference has already been made to the hexone bases, 

 the protones and the protamines. To that account the 

 following facts may be added. The protamines resemble 

 other proteids in being laevorotatory, and have a toxic 

 action similar to that of the albumoses. It is worthy of 

 mention that, although the salts of the protamines with 

 mineral acids are laevorotatory, those of the hexone base, 

 histidin, are dextrorotatory. The protamines also resem- 

 ble the proteoses and peptones in not being coagulated 

 by heat. 



Intermediate between the protamines and the native 

 proteids lies a somewhat ill-defined class of proteids 

 termed the histones. These have a well-marked basic 

 character, being precipitated from their solutions by the 

 addition of ammonia. They are not precipitated by 

 heat unless a neutral salt of the alkalies be present, and 

 even under those conditions they are incompletely pre- 

 cipitated. Within the organism they are never found in 

 the free form ; but always in combination with some 

 other organic group, usually either nucleic acid or a pig- 

 ment. It is asserted that they are occasionally found in 

 the urine. 



Their chemical properties place them in a class interme- 

 diate between the protamines and the simple native 

 proteids. On account of their tendency to form com- 

 pounds with other proteids, they appear to be well fitted 

 to serve as precursors of the more complex forms of pro- 

 teid. In neutral solutions they give ^precipitates with 

 egg-albumin, serum-globulin, and caseinogen containing 

 the two components in a fixed quantitative relation. 



The most important recent advances in our knowledge 

 of the proteoses are due to the work of Hofmeister and 

 his pupils. They have applied the method of fractional 

 precipitation by means of ammonium sulphate and of zinc 

 sulphate to the separation of the proteoses resulting from 

 the peptic digestion of various proteids, and, although it 

 has not yet been found possible to separate by these 

 means chemically distinct bodies, the complete separation 

 of the proteoses into chemical individuals may be looked 

 upon as a probable attainment in the near future. The 

 chief difficulty of the separation is due to the fact that 

 the proteoses, being all either of an acid or basic charac- 

 ter, tend to unite together so as to form salt-like com- 

 pounds. Only the briefest summary of the more recent 

 results can be given here. 



The proteoses may be divided into three classes. 



The first class yields, on farther hydrolytic decompo- 

 sition, a large quantity of monamido- and diamiao-acids 

 of the fatty series. It also contains a benzene radicle 

 in which none of the hydrogen atoms are substituted for 

 hydroxyl and a relatively large proportion of both 

 loosely and firmly combined sulphur. It corresponds in 

 NO. 1627. VOL. 63] 



type to Kiihne's anti-group and, from the large proportion 

 of diamido-acids which it yields, may be regarded as 

 more closely allied to protamine than either of the two 

 other classes. It is very resistant to hydrolytic agents. 



The second class contains loosely and firmly combined 

 sulphur, a benzene radicle in which one hydrogen atom 

 has been substituted for hydroxyl and yields a relatively 

 small quantity of monamido- and diamido-acids of the 

 fatty series. It easily undergoes hydrolytic decomposi- 

 tion, and is termed the hemi-group. 



The third class has been less thoroughly investigated. 

 It is distinguished from the two former classes by the 

 presence of a carbohydrate radicle, and is apparently 

 absent from the molecule of many native proteids. One 

 may regard the molecules of the majority of native 

 proteids as being built up by the union of these three 

 groups in varying proportions. 



The chemical nature of the peptones is still the subject 

 of much controversy. They are characterised mainly by 

 not being precipitated by saturation of their acid solutions 

 with ammonium sulphate, by giving a well-marked biuret 

 reaction, and by yielding on farther hydrolytic decom- 

 position the hexone bases amongst other products. 



A detailed account of the individual native proteids is 

 next given. Then there follows a description of the com- 

 pound proteids which consist of one or more molecules 

 of a simple proteid united with some other body, which 

 may be either nucleic acid, chondroitinsulphuric acid, a 

 pigment, or a nitrogenous derivative of the polysac- 

 charides probably bearing the same relation to muco- 

 samine or glucosamine as starch does to glucose. Cohn- 

 heim places the nucleoalbumins amongst the simple pro- 

 teids, and suggests phosphoglobins as a more suitable 

 name for the group. 



The book terminates with a description of the chemical 

 and physical properties of the albuminoids. 



In conclusion, one cannot but feel that Dr. Cohnheim 

 has earned the gratitude of both chemists and physio- 

 logists by his thorough review of the present state of 

 knowledge of the chemistry of the proteids. In no other 

 branch of chemistry is the literature scattered throughout 

 so many journals of very diverse branches of science, 

 and this makes the task of reviewing the literature a 

 most arduous one. 



As a work of reference the book is indispensable to all 

 workers in physiological chemistry. J. A. MiLROY. 



MODERN LENS MAKING. 

 Contributions to Photographic Optics. By Dr. Otto 

 Lummer. Translated and augmented by Prof. 

 Silvanus P. Thompson, F.R S. Pp. xi -f 135. 

 (London : Macmillan and Co., Ltd., 1900.) 



DR. LUMMER and Prof. Thompson have given us 

 in the above volume a thoroughly practical treatise 

 on that part of optics with which it deals, and the book 

 does much to prove the truth of a statement of the 

 translator's preface : " In fact the science of the best 

 optical instrument-makers is far ahead of the science of 

 the text-books." 



The history of the book is interesting. Dr. Lummer, 

 when working up the subject of photographic optics for 

 a new edition of Miiller-Pouillet's text-book of physics 



