A Text Book of Physiology Author:Michael Foster Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. Excerpt from book: Section 3Sec. 4. The Quantity Of Blood, And Its Distribution In The Body. The total quantity of blood present in an animal body is estimated in the following way. As much blood as possible is... more » allowed to escape from the vessels ; this is measured directly. The vessels are then washed out with water or normal saline solution, and the washings carefully collected, mixed and measured. A known quantity of blood is diluted with water or normal saline solution until it possesses the same tint as a measured specimen of the washings. This gives the amount of blood (or rather of hxmoglobin) in the measured specimen, from which the total quantity in the whole washings is calculated. Lastly, the whole body is carefully minced and washed free from blood. The washings are collected and filtered, and the amount of blood in them estimated as before by comparison with a specimen of diluted blood. The quantity of blood in the two washings, together with the escaped blood, gives the total quantity of blood in the body. Estimated in this way, the total quantity of blood in the human body may be said to be about -^th of the body-weight. There are several sources of error in the above method. One is that venous blood has less colouring power than arterial blood. This has been met by Gscheidlen by poisoning the animal with carbonic oxide, by which all the haemoglobin is reduced to one state, and therefore has throughout the same colouring power. The quantity of haemoglobin in the muscular fibre itself is a source of error, but probably a very slight one. The difficulty of getting a clear infusion of the minced tissues is more serious. According to Ranke' the total blood in the body of a rabbit amounts to -j^ of the body-weight, in a dog to textit{-fa, in a cat to ^j, in a frog to 11y. The blood* is distributed as follows in ro...« less