NA TURE 



385 



THURSDAY, FEBRUARY 26, 1903. 



THE LIVING SUBSTANCE— A THEORY. 



Die Biogen-hypothese. By Prof. Max Verworn. Pp. 



iv+114. (Jena: Fischer, 1903.) Price 2.50 marks. 



THE author of the well-known work on " Allgemeine 

 Physiologie " is always interesting in his physio- 

 logical writings, whether one admits the validity of his 

 conclusions or not ; and the volume before us, though 

 highly speculative in its nature, cannot fail to attract 

 attention, no less on account of the intrinsic importance 

 of the subject than by reason of the lucidity with which 

 a difficult topic is handled. 



The Biogen-hypothese is nothing less than an attempt 

 to frame a working hypothesis that shall render intelli- 

 gible the modus operandi of a living organism and to 

 explain in a comprehensive manner the general nature 

 of the physical and chemical processes involved. Such 

 an explanation, as the author himself insists, can only be 

 regarded as a temporary expedient in the present con- 

 dition of our knowledge, but the author of a theory or 

 hypothesis is amply justified in propounding it if he is 

 enabled thereby to indicate definite lines of investigations, 

 whatever the influence the results thereby obtained may 

 exercise on the theory itself. 



The various hypotheses that have been put forward to 

 account for the facts of metabolism are briefly discussed 

 and the nature of the respiratory process is specially 

 considered. It seems quite clear from the results of 

 numerous investigators that whatever the nature of the 

 sequence of chemical events, the carbohydrates are 

 proximately the substances that are most intimately 

 affected. These carbohydrates might be derived directly 

 from the store of accumulated reserve products, or an 

 analogous atom group might be split off from the more 

 complex proteid-like bodies. On the whole, the latter 

 seems the more probable view, and thus dissimilation 

 and assimilation form a constantly oscillating series of 

 phenomena that give rise to the processes described as 

 metabolism. 



The biogen is regarded by Verworn as a real chemical 

 or physical entity, consisting of various groups of atoms 

 held together round a central benzene nucleus. Dis- 

 similation, or katabolism, occurs when certain atom- 

 groups are split off from the biogen, and normally these 

 represent carbohydrates or some similar bodies, a view 

 which is by no means new and one that finds support, 

 for example, in the behaviour of muscle when it is made 

 to do work. For it is well known that the excessive amount 

 of carbon dioxide excreted in such circumstances is not 

 accompanied by a correspondingly increased excretion 

 of nitrogenous waste-products. On the contrary, the 

 nitrogenous remainder of what Verworn terms the biogen 

 regenerates itself by seizing upon the available sugars or 

 other carbohydrates. A distinction is drawn between 

 this "functional" dissimilation and the "destructive" 

 dissimilation that follows on extreme starvation ; for in 

 the latter case the nitrogen-containing remainder of the 

 biogen undergoes further decomposition, and then the 

 simpler groups thus produced no longer possess the 

 NO. 1739, VOL. 67] 



faculty of regeneration at all and so are unable to 

 reproduce the living substance once more. 



As to the cause of the lability of the biogen, Verworn 

 strongly champions the view that it is the result of the 

 incorporation of oxygen in the molecule, and that when 

 irritability ceases, on arresting the supply of this gas, it is 

 not due to the possible inhibitory action of the accumu- 

 lating waste products, but that in the absence of oxygen 

 the conditions of adequate lability are not provided. The 

 arguments are largely based on the behaviour of frogs 

 that have been poisoned by strychnine and in which an 

 artificial circulation by means of salt solution is main- 

 tained. This can be so arranged as to provide or with- 

 hold oxygen from the tissues. In the latter case, 

 stimulation ceases to excite contraction in the muscles, 

 though on readmitting oxygen, tetanus is easily produced 

 on the application of suitable stimuli. If a long interval 

 of time is allowed to elapse during which no food is 

 being conveyed to the tissues, starvation, and consequent 

 reduction in the number of labile biogens, ensues. 

 Hence stimuli gradually provoke weaker and weaker re- 

 sponses. If once more the supply of oxygen is cut off, 

 loss of excitability again supervenes, but this passes 

 away again on readmission of oxygen. Verworn seems 

 to conclude that because this return of excitability re- 

 curs at once, both in the unstarved and starved tissue, 

 the inhibition effect of the deprivation of oxygen 

 cannot be ascribed to the accumulation of waste pro- 

 ducts, since in the former case this should have been of 

 much greater magnitude in correspondence with the 

 much larger amount of waste substances, and, therefore, 

 the role of the oxygen must have been that of a labilising 

 agent, directly producing the" condition for explosive 

 decomposition in the active biogens. But it is not shown 

 whether the influence of waste products upon the hypo- 

 thetical biogens may not be a proportionate one, in which 

 case there would be perhaps no very obvious reason why 

 any difference should be looked for in the two cases. 

 Moreover, it is quite clear that the free oxygen does 

 oxidise harmful waste products and reduce them to a 

 form {e.g. carbon dioxide and water) in which they may 

 be either innocuous or at least readily escape from the 

 .tissues. The accumulation of alcohol in plant tissues in 

 the absence of oxygen is a case in point, and readmission 

 of oxygen has the immediate result of increasing the out- 

 put of carbon dioxide at the expense of the alcohol 

 abnormally present in the tissues. 



The biogen hypothesis gives a plausible account of 

 growth and the production of fresh living material by 

 supposing that the molecule is capable of polymerisation 

 and then of falling into simpler substances once more. 

 But this view would seem further to imply that the more 

 highly polymerised bodies do not differ essentially in 

 their properties from the more simple ones. In endeavour- 

 ing to locate the seat of the biogens in the cellular organ- 

 isation, it is concluded that they exist in the cytoplasm 

 but not in the nucleus. The evidence for this is based on 

 observations adduced to show that enucleated protoplasm 

 can exhibit metabolic activity, and further, that the 

 oxidative charges are more especially obvious in the 

 cytoplasmic, rather than in the nuclear, constituents of 

 the cell. But perhaps one may reasonably question the 



