594 GENERAL METABOLISM. [CH. xxxix. 



few days all the floating capital was consumed ; (2) the effect 

 of feeding with a mixture of gelatin and proteid was supposed to 

 be due to the fact that gelatin was able to replace "floating 

 proteid," but not " tissue proteid." 



This theory of Voit's, ingenious and plausible at first sight, 

 has met with but little general acceptance, because so many 

 observed facts are incompatible with it. 



Sir Michael Foster writes as follows : " The evidence we 

 have tends to show that in muscle (taking it as an instance of 

 a tissue) there exists a framework of what we may call more 

 distinctly living substance, whose metabolism, though high in 

 quality, does not give rise to massive discharges of energy, and 

 that the interstices, so to speak, of this framework are occupied 

 by various kinds of material related in different degrees to this 

 framework, and therefore deserving to be spoken of as more or 

 less living, the chief part of the energy set free coming directly 

 from the metabolism of some or other of this material. Both 

 framework and intercalated material undergo metabolism, and 

 have in different degrees their anabolic and katabolic changes ; 

 both are concerned in the life of the organism, but one more 

 directly than the other. We can, moreover, recognise no sharp 

 break between the intercalated material and the lymph which 

 bathes it ; hence such phrases as ' tissue proteid ' and ' floating 

 proteid ' are undesirable if they are understood to imply a sharp 

 line of demarcation between the ' tissue ' and the blood or 

 lymph, though useful as indicating two different lines or degrees 

 of metabolism." 



Sir John Burdon-Sanderson writes as follows : " The production 

 of urea and other nitrogenous metabolites is exclusively a func- 

 tion of ' living material ' ; and this process is carried on in the 

 organism with an activity which is dependent on the activity 

 of the living substance itself, and on the quantity of material 

 supplied to it. No evidence at present exists in favour of a 

 ' luxus consumption ' of proteid." 



Professor Hoppe-Seyler, after stating that he can make out no 

 clear distinction between the two varieties of proteid from Voit's 

 own writings, proceeds as follows : " Voit states that the circu- 

 lating proteid is no other than that which is dissolved in the tissue 

 juice, which is derived from the lymph-stream, and ultimately 

 from the circulating blood. He (Voit) further says : 'As soon as 

 the proteid of the blood-plasma leaves the blood-vessels, and circu- 

 lates among the tissue elements themselves, it is then the proteid 

 of the nutrient fluid or circulating proteid. It is no longer proteid 

 of the blood-plasma, nor yet is it the proteid of the lymph-stream.' 



