64 



Dr. A. B. Garrod. 



[Feb. 22 r 



Part I. — The results of many fresh observations, which have been 

 made on the composition of the urinary excretion in several of the 

 lower animals, are given. 



The physical and microscopic characters of the semi -solid urines of 

 birds and reptiles and invertebrata have been investigated at length, 

 and it is shown that the urate is always in the form of spherule 

 aggregates, made up of a great number of smaller spherules ; that 

 each of these is united with or contained in a cell of colloid matter, 

 and that when treated with water and weak carbonated alkaline 

 solutions, this solid urine swells up to very many times its original 

 bulk. 



The results, of an investigation into the chemical composition of 

 such urates are stated in a tabular form. 



An examination of the blood of man and many mammals and birds 

 and reptiles, especially in relation to uric acid, has been made, and the 

 results are given. 



Part II. — The different views as to the origin of uric acid in the 

 animal body are discussed, and an endeavour is made to explain the 

 various apparent difficulties of the subject. The following points are 

 especially dwelt upon : — 



(<x.) The very varying amounts of uric acid thrown out by different 

 animals in relation to their total nitrogenised elimination. 



(6.) The excessively large excretion of uric acid by a great number 

 of the lower animals, as birds, reptiles, and invertebrate animals, 

 compared with the weight of their bodies. Under this head it is 

 shown that whereas man excretes, on an average, rroVooth P ar ^ °^ 

 his weight of uric acid per diem, a bird often excretes as mucb as 

 Y^^th part of its weight during the same period ; in other words, a 

 bird throws out from its kidneys during a given time a thousand 

 times more uric acid than a man. 



The effect of uric acid and its salts upon the urinary excretion, when 

 introduced into the animal economy, either with food or injected into 

 the veins, is discussed, and it is shown that the kidneys do not possess 

 the power of filtering uric acid from the blood when it is present in 

 that fluid. 



The different conditions in which uric acid is found in the kidneys 

 and urinary excretions under varying circumstances, and also in the 

 blood and tissues of the body, are dwelt upon. 



The presence of uric acid in the urinary excretion of the young of 

 the herbivorous "mammal, and its usual absence in the case of the 

 adult of the same species, are investigated ; it is also shown that, 

 whereas in the kidneys ammonia is combined with the acid, in the 

 blood it is found as urate of sodium, as also when deposited in the 

 different tissues of the body. This latter phenomenon is explained in 

 full. 



