PHILOSOPHICAL SOCIETY OF WASHINGTON. 75 



incomplete that further inquiry in each direction is greatly to be 

 desired. 



This is particularly the case with regard to the chemical ques- 

 tions connected with the metabolism of the brain. In the first 

 place our knowledge of the chemical composition of brain-sub- 

 stance is still in its infancy. The view that its characteristic in- 

 gredient is the phosphorized nitrogenous body described in 1865 

 by Liebreich under the name of protagon has been strongly con- 

 troverted by Diaconow, Hoppe-Seyler, and Thudicum, while recently 

 it has been reaffirmed by Gamgee, and Blankenhorn. 45 But even 

 should this view turn out to be well founded, we have yet every- 

 thing to learn with regard to the transformations protagon under- 

 goes during functional activity, and the nature of the resulting 

 waste products. 



Long before Liebreich announced the existence of protagon, 

 however, the attention of the physiological chemists had been 

 directed to the prominence of phosphorous as an element in 

 the composition of the cerebral substance, and it had been sug-^ 

 gested that a part of the phosphoric acid excreted in the urine 

 might be derived from the metabolism of the brain. As early as 

 1846 Bence Jones 46 had observed an excess of phosphatic salts in 

 the urine during certain brain diseases, notably acute inflammations, 

 and an observation published in 1858 by Mosler 47 appeared to 

 indicate that a similar excess followed intellectual activity. 



Byasson [1868] in his essay on the relation between cerebral 

 activity and the composition of the urine, 48 reports a number 

 of urinary analyses which support the view that the excretion 

 of alkaline phosphates by the kidneys is habitually increased 

 during mental work. This opinion has also received a certain 

 degree of support from the more recent papers of Zuelzer 49 and 

 Struebling; 50 nevertheless it is impossible to study the detailed obser- 

 vations upon which it is based without feeling how meagre and 

 unsatisfactory the evidence relied upon really is. It is at best only 

 sufficient to indicate the importance of further inquiry, and to sug- 

 gest the necessity of avoiding certain obvious errors of method 

 which complicate and obscure the results of the investigations 

 hitherto made. 



The opinion that mental effort is accompanied by an increase in 

 the temperature of the brain was first propounded by Lombard in 

 1867. Using a delicate thermo-electric apparatus of his own con- 



