^278 A MANUAL OF PHYSIOLOGY 



the hydrogen and carbon of its substance to form water and carbon 

 dioxide. Calculate the respiratory quotient (p 225). 



7. Section of both Vagi. Proceed as in experiment 24, p. 190, 

 but use an ordinary rabbit ; and instead of cutting the sympathetic, 

 pass threads under both vagi, divide them, and sew up the wounc. 

 An induction coil is not required, unless the student has any diffi- 

 culty in deciding which nerve is the vagus. The point may be at 

 once settled by stimulating the nerves before division. Stimulation 

 of the vagus will cause slowing or stoppage of the heart, and there- 

 fore of the pulse in the carotid, and quickening of respiration. 

 Stimulation of the sympathetic will have neither of these effects. 

 A dog may also be used, and the vago-sympathetics divided. Count 

 the pulse and the rate of respiration before and after the section of 

 each nerve, and observe carefully any change that may occur. Also 

 note whether the depth of the breathing is affected. The anima) 

 must be looked at once at least on the day of the operation, and its 

 behaviour carefully observed. It should be seen daily thereafter so 

 long as it survives. A rabbit does not usually live much more than 

 twenty-four hours. 



As soon after death as possible, make an autopsy, observing 

 especially the state of the lungs. Harden portions of the lungs that 

 appear to contain the most exudation in Miiller's fluid (ten times as 

 much fluid as tissue). Change the fluid next day, and again at the 

 end of a week. In three or four weeks wash out the Miiller's fluid 

 under the tap, and transfer the tissue to 90 per cent, alcohol. After 

 a lew days it is to be prepared for cutting by being passed succes- 

 sively through absolute alcohol (two days), absolute alcohol anci 

 ether mixture (two days), thin celloidin (two or three days), Lhick 

 celloidin (one day). Fasten on vulcanized wood-fibre and cut 

 sections with a sliding microtome, moistening the knife with 8^ per 

 cent, alcohol. Stain, mount, and examine under the microscope. 

 Note the exudation in the alveoli, and make drawings. Write a 

 report of your complete experiment. 



