290 RESPIRATION 



tory and expiratory phases are now forced, dyspnea. The movements con- 

 tinue to increase, and the muscles of the neck, larynx, mouth, and nostrils 

 now take part. There is rather a sudden decrease in the respiratory move- 

 ments, an extension of the limbs, and gasping movements of the mouth, after 

 which the animal remains quiet, death being produced by asphyxia. 



13. Respiratory Interchange, Calorimetry. The experiments are 

 conducted in such a manner that comparative analyses may be made between 

 the air inspired and that expired. Generally an animal is placed in a cham- 

 ber, called the respiratory chamber, which is then closed except for two 

 openings, one for the entrance of the inspired air, the other for the escape 

 of expired air. Some form of pump is used for renewing the air in the 

 chamber. . Both the inspired and expired air is made to pass through agents 

 which will absorb the contained carbon dioxide, such as baryta water or soda 

 lime, and in turn through agents which will absorb the watery vapor. When 

 the experiment is completed the differences between the two are determined. 

 The difference in oxygen has to be calculated, and is open to error. 

 The famous respiratory chamber of Pettenkofer is large enough to per- 

 form such experiments on man, and is of very elaborate construction. 

 But the most perfect apparatus assembled for this purpose is the respira- 

 tion calorimeter of Atwater constructed for man, and the respiration ap- 

 paratus of Armsby for cattle. 



