IN DISEASES. 459 



in the globular form, but also in the peculiar baton-like shape in 

 which it occurs in the Euphorbiacese. These excrements are 

 especially rich in oxalate of lime,, which is not produced directly 

 from the ingesta ; for I have found them in the biliary tubes of 

 caterpillars. Although the intestinal juices and the contents of 

 the stomach of caterpillars have always a very strong alkaline 

 reaction, the excrements are for the most part neutral, and indeed 

 sometimes have an acid reaction. In the latter case, we often find 

 that they contain very beautiful crystals of uric acid ; the uric acid, 

 however, generally only appears in very small quantity in the 

 excrements of caterpillars. Different parts of plants, as, for 

 instance, the spiral vessels, may be very distinctly observed in 

 these excrements, which are so poor in nitrogen that, as an average 

 of three analyses, I found only 0'362^ of this element in the 

 matters discharged by the silkworm, while the leaves of Morus 

 nigra contained 4*560^. 



We have already spoken, in vol. i., p. 1/3, of the occurrence of 

 guanine in the excrements of spiders. Seeing that this substance 

 is present here as well as in guano, it is not improbable that 

 guanine may also occur in the excrements of birds and in those 

 of most insects, especially since the researches of Will and Gorup- 

 Besanez* have rendered it probable that this substance is also 

 present in the green organ of the craw-fish. 



Guano, that much-prized article of commerce, which is the 

 product of the slow decomposition of the excrements of certain 

 sea-fowl, has been very frequently analysed, and has been found to 

 be very variously composed according to the place from whence it 

 was obtained; its principal constituents are guanine, urate of 

 ammonia, oxalate of ammonia, phosphate of lime, phosphate of 

 magnesia and ammonia, and oxalate of lime ; we likewise find the 

 remains of vegetable substances; and there is one variety which 

 contains the most beautiful siliceous shields of infusoria pertaining 

 to the Bacillariae. 



We now proceed to the changes which the urine undergoes in 

 disease ; and we will first notice the characters which are impressed 

 upon this secretion in fever, that is to say, in that group of 

 symptoms which accompany almost all acute diseases. Febrile 

 urine is generally more deeply coloured than usual (being of a red 

 or reddish tint), has a stronger odour, a higher specific gravity, 

 and a more decided acid reaction. As long as the fever continues, 

 less than the normal quantity of urine is generally secreted by the 

 * Gel. Auzeigen d. k. bair. Ak. d. Wiss. 1848. S. 825828. 



