BLOOD. 349 



Spider's webs were almost wholly soluble in six times their 

 weight of nitric acid, carbonic acid and deutoxide of azote 

 being disengaged. The solution gave sulphate of lime, and the 

 bitter principle of Welter. 



PART II. 



OF THE LIQUID PARTS OF ANIMALS. 



THESE consist of blood and of the various liquid secretions. They 

 are numerous. But many of them cannot be procured in a state 

 of purity. We shall treat of them in succession in the following 

 chapters. 



CHAPTER I. 



OF BLOOD. 



BLOOD is a well known fluid that circulates in the veins and 

 arteries of man, and the more perfect animals. The quantity in 

 a moderate- sized man is about 26 Ibs. avoirdupois. Its colour 

 is red, and it has a peculiar smell, which has been termed by 

 physiologists fragrant and alliacious. When examined in the 

 living animal by a microscope, it has the appearance of a green- 

 ish yellow serous liquid, in which a great number of red colour- 

 ed globules are floating. When drawn out of the living body 

 and left at rest, the globules fall to the bottom, in consequence 

 of their greater specific gravity, and coagulate into a firm gela- 

 tinous red coagulum, called the crassamentum or clot of the blood ; 

 while the greenish yellow serum floats above it. 



One of the first persons who attempted a chemical exami- 

 nation of the blood was Mr Boyle in his Memoirs for the Na- 

 tural History of Extravasated Human Blood, published in 1684. 

 He showed that dried human blood is very combustible, burning 

 with a clear yellow flame. He found the specific gravity of the 

 blood of a healthy man to be 1-118. It was coagulated by al- 



