430 EXCRETION. 



elaborate series of observations upon Mr. "VVeston, the pedestrian. Of these we can only 

 give here a brief summary. Mr. Weston walked for five consecutive days as follows : 

 First day, 92 miles; second day, 80 miles; third day, 57 miles; fourth day, 48 miles; 

 fifth day, 40| miles. The nitrogen of the food was compared with the nitrogen excreted 

 for three periods ; viz., five days before the walk, five days walking, and five days after 

 the walk. ' A trusty assistant was with Mr. Weston day and night for the fifteen days; 

 the food was weighed and analyzed ; the excreta were collected ; and other observations 

 were made during the entire period. The analyses were made independently, under the 

 direction of Prof. E. O. Doremus, who had no idea of the results until we had classified 

 and tabulated them. The conclusions were most decided, and, as far as possible, all the 

 physiological conditions were fulfilled. As regards the proportion of nitrogen eliminated 

 to the nitrogen of the food, the general results were as follows : 



For the five days before the walk, with an average exercise of about eight miles daily, 

 the nitrogen eliminated was 95*53 parts for 100 parts of nitrogen ingested. For the five 

 days of the walk, for every hundred parts of nitrogen ingested, there were discharged 

 174-81 parts. For the five days after the walk, when there was hardly any exercise, for 

 every hundred parts of nitrogen ingested, there were discharged 91 '93 parts. During 

 the walk, the nitrogen excreted was in direct ratio to the amount of exercise ; and, what 

 was still more striking, the excess of nitrogen eliminated over the nitrogen of food almost 

 exactly corresponded with a calculation of the nitrogen of the muscular tissue wasted, 

 as estimated from the loss of weight of the body. Full details of the method of investi- 

 gation, the processes employed, etc., are given in our original paper. 



Influence of Mental Exertion. Although the influence of mental exertion upon the 

 composition of the urine has not been very closely studied, the results of the investiga- 

 tions which have been made upon this subject are, in many regards, quite satisfactory. 

 It is a matter of common remark that the secretion of urine is often modified to a 

 considerable extent through the nervous system. Fear, anger, and various violent emo- 

 tions, sometimes produce a sudden and copious secretion of urine containing a large 

 amount of water, and this phenomenon is often observed in cases of hysteria. Intense 

 mental exertion will occasionally produce the same result. We have often observed 

 a frequent desire to urinate during a few hours of intense and unremitting mental labor ; 

 and, on one occasion, being struck with the amount of urine voided, it was found, on 

 examination, to present scarcely any acidity, and a specific gravity of about 1002. The 

 interesting point in this connection, however, is to observe the influence of mental labor 

 upon the elimination of solid matters, as contrasted with the amount of excretion during 

 complete repose, the conditions of alimentation in the two instances being identical. 



In a very interesting work upon the influence of cerebral activity upon the composi- 

 tion of the urine, Byasson found that by mental exertion the quantity of urine was 

 increased ; the amount of urea was also increased ; the phosphoric acid was increased 

 about one-third ; the sulphuric acid was more than doubled ; and the chlorine was 

 nearly doubled. 



These facts have an important bearing upon our knowledge of the effects of mental 

 exertion upon the process of disassimilation of the nervous tissue. They show that nearly 

 all of the solid principles contained in the urine are increased in quantity by prolonged 

 intellectual exertion, but they fail to point to any one excrementitious principle, either 

 organic or inorganic, which is specially connected with the physiological wear of the 

 brain. It has been assumed that elimination of the phosphates, increased out of propor- 

 tion to the increase of the other solid matters of the urine, is one of the constant effects 

 of intellectual effort ; but this view is not sustained by direct physiological experiments 

 or by facts in pathology. We have already discussed this question somewhat elaborately, 

 under the head of the phosphates of the urine. 



