RAPIDITY OF THE CIRCULATION. 75 



The action of the heart may be taken as a general index of this. The following 

 table has been drawn up from the researches of Dumas, Prevost, Miiller, and Simon. 



Rapidily of CircukUion in Different Animals. 





Number of beats per minute. 



Til tllP Ati3'ilfi]fiy"?tQ 



X li til Li U^l- I U 1 1 1 Ho • 1 • • • • • 



1 



Oill [)........ 



90 



J; loUt/b gcllclaliy ....... 



20 24 



VTlCCll XUaLl ....... 



\ i 



Jj IV^ri ^cUcltlliy ....... 



nhnnt PiO 



JL i^UOIl ........ 



loo 



v^UIlluluU xlcll ....... 



1 in 



J_/ULK ........ 



X 1 o 



' ^ 1? o ir fi 11 



XVilVUlL ........ 



X 1 o 



" Heron ........ 





" Birds generally ....... 



100—200 



" Ox 



38 



" Horse ........ 



56 



" Sheep ........ 



75 



" Goat ........ 



84 



" Hare ........ 



120 



" Guinea-Pig ....... 



140 



" Dog ........ 



90—95 



"Cat ....... . 



100—110 



" Ape (Simia Callitnclie) . . 



90 



" Human embryo ....... 



150 



" " just after birth ..... 



130—140 



" Human being during first year ..... 



130—115 



" " during second year ..... 



115—100 



" " during third year ..... 



100—90 



" " about seventh year ..... 



90—85 



" " about fourteenth year .... 



85—80 



" " in the middle period of life 



•75— to 



" " in old age . ..... 



65—50 



" Mammals generally ...... 



38—140 



This table shows that the rapidity of the circulation corresponds with the struc- 

 ture, habits, age, and development of animals. 



If the vital forces are of a low grade, either from original conformation or the 

 depressing influences of old age, the circulation is correspondingly sluggish and 

 feeble. 



As the fluids and solids of animals become more highly elaborated and developed, 

 the action of the heart and circulation of the blood become more rapid and vigorous. 



The next consideration is that of the structure of the respiratory system in the 

 different orders of animals. 



One of the essential conditions of the life of all organized beings, whether vege- 

 table or animal, is a supply of oxygen. The modes in which oxygen is brought 

 in contact with the fluids and solids of organized structures, vary with the develop- 

 ment and peculiar manner of life of the dilTerent classes of animals. 



In the lowest classes of the Invertebrata, in which the digested matters pass 

 directly from the stomach into the different structures of the body, and become 

 integral parts of the animal; we find no special circulatory system, and respiration 



