the Carbon exhaled by tJte Lungs. 435 



It is of interest to note that during this period of iudirt-ot 

 action the other phsenomena following the introduction of food 

 are observed, as, for example, the increased pulsation and greater 

 distribution of heat to the surface, all of which take place before 

 the transformation of food is fully completed. 



3. There is no relation whatever between the amount of this 

 indirect influence and the quantity of carbon which they con- 

 tain. 



4. Nearly every substance in which this indirect influence is 

 considerable contains nitrogen. (Sugar is the principal exception 

 with which I am at present acquainted.) With the exception of 

 tea, the greatest influence is found when nitrogen is associated 

 with mucTi carbon, as in the cereals and milk. I have called 

 these nitrogenous matters and sugar " respiratory excitants." 



These facts, added to the great and quick influence of sugar 

 and its rapid conversion into acid, lend probability to the view 

 that, in some instances at least, it is at the stage of conversion 

 into acid, and by the acid, that this influence is exerted. 



5. It i.s a subject worthy of reflection, that whilst the admi- 

 nistration of carbonaceous food is followed by and induces an in- 

 creased evolution of carbon, the latter is not directly supplied 

 from the former; and moreover that every indirect action of the 

 food is still not due to the carbon, nor is in relation to the quan- 

 tity of carbon contained in it. What, then, is the course which 

 the carbon pursues before it is really eliminated from the body ? 

 Is it possible that in any case the aliment may be transformed iu 

 the blood, and be ultimately eliminated without having been an 

 integral part of any solid tissue ? or must all food be transformed 

 into living tissue, and then be resolved before it quits the system ? 

 or can both these processes exist at the same time in reference to 

 the same food, or one be the course pursued by one kind of food 

 and the other by another kind of food ? 



6. Is there any fallacy in these reflections in regarding the 

 ina-eased quantity of carbonic acid and omitting the constant 

 quantity, since the increase is temporary and not more than half 

 of the constant or minimum quantity ? It is highly probable 

 that each must be considered apart; but the periodic increase 

 is so important as to be essential to life, since the constant or 

 minimum quantity is that which also occms in entii'e abstinence 

 from food, — a condition which we know to be inimical to life. 



7. When a substance causes an increased discharge of carbonic 

 acid from the blood, is the process by which that carbonic acid 

 is again supplied materially quickened ? After the increase has 

 proceeded for a definite but short period, it is followed by a de- 

 crease which proceeds more or loss quickly until the minimum 

 quantity is again attained, as though the carbonic acid had been 



2 F2 



