430 EXCRETION". 



elaborate series of observations upon "Weston, the pedestrian. \ Of these we can here 

 give only a brief summary. 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 by a com- 

 petent chemist 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 nitro- 

 gen 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 92*82 parts for 100 parts of nitrogen ingested. For the five 

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

 153-99 parts. For the five days after the walk, when there was hardly any exercise, for 

 every hundred parts of nitrogen ingested, there were discharged 84-63 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. 



In 1876, Dr. F. W. Pavy made a series of observations upon Weston, similar to 

 those which we made in 1870. The actual results of these observations did not differ 

 materially from our own; but Dr. Pavy's interpretation of his results was entirely 

 different. Taking Dr. Pavy's actual figures, however, we cannot regard his experiments 

 as conflicting at all with -our own conclusions, and, in point of fact, -his observations 

 fully confirm those which we published in 1871. We have given an elaborate review 

 of the recent observations in a little work on The Source of Muscular Power, published 

 in 1878, in which we have made a careful comparison of Dr. Pavy's figures with our own. 



In Dr. Pavy's experiments, the figures certainly show an increase in the proportionate 

 elimination of nitrogen, due to the excessive muscular work. 



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. 



