Feb., 1912. Mammals of Illinois and Wisconsin — Cory. 21 



^ • 



Origin of arteries from the aortic arch, illustrating three of the various types: i. Ox; 2, Lion; 

 3, Man. (After Owen.) Heart of man: 4, aorta; 5. pulmonary artery; 6, superior vena cava; '7, pul- 

 monary veins; 8, right auricle; 9, inferior vena cava; 10 right ventricle; 11, left auricle; 12 left' ventri- 

 cle; 13 aorta; 14, innominate artery. (After Tenney.) 



directly from the aorta, or again there may be a right and left 

 "innominate," from which arise the respective carotid and brachial 

 arteries, as in some of the Bats and Insectivores. The circulatory 

 system is much further diversified in many other mammals, but 

 enough has been said regarding the subject. 



The Lungs — The lungs of a mammal differ from those of the lower 

 vertebrates by being separated from the abdominal cavity by a 

 diaphragm. They are spongy masses made up of numerous air pass- 

 ages and cells surrounded by a capillary network in which the blood, 

 in passing through the lungs, absorbs oxygen, at the same time 

 giving off carbon dioxide. In terrestrial forms they are more or less 

 extensively lobated in form and are often not symmetrical, the num- 

 ber of lobes differing in the two lungs of the same animal. 



Blood — The blood of mammals is red and warm, varying in tempera- 

 ture in different species under nonnal conditions from a few degrees 

 below to a few degrees above ioo° Fahr. The corjiuscles are of two 

 kinds: the colored non-nucleated flattened disks, having a circular 

 outline*; and the less numerous "white corpuscles," which are color- 

 less and nucleated. The .size of the red non-nucleating blood cor- 

 puscles varies in different mammals, and this fact is often of im- 

 portance in criminal trials as an aid in identifying human blood ; but 

 in such cases, while it is very often possible to determine that the 

 blood in question is not human, by this test alone, it is not always 

 possible to be absolutely certain that it is. For example, the diam- 

 eters of the circular blood corpuscles in species of Deer range from 

 oo^oo to 12000 of an inch; those of domestic Sheep are li-.ioa; of the 

 Horse Wo o ; while in Man they usually measure from about 3 o'o to 

 :'. /go, but occasionally they are smaller, cases having been recorded 



* Exceptions to this are found in the Camels, Llamas, and a few others, in which 

 they are elliptical in outline, as in most of the lower vertebrates. 



