318 EXPERIMENTAL PHARMACOLOGY 



heart and a small amount can easily pass back from the 

 pulmonary artery into the right ventricle. This may kill 

 the heart immediately. Could you use hirudin for this pur- 

 pose? "What objections could you offer? 



The average group of students will not get more than 

 tAvo good pulmonary pressure records from one dog. If 

 the animal is still in suitable condition inject five cubic cen- 

 timeters of barium chloride solution (one-half per cent). 

 What conclusions can you draw? In how many ways may 

 drugs affect the pulmonary blood-pressure? How many 

 of these does your experiment illustrate? "\Vhat differ- 

 ences are there betAveen the systemic and pulmonary cir- 

 culation? Historically Avhich of the systems Avas first dis- 

 coA T ered? By Avhom? Kill the dog Avith a dose of barium. 



EXPERIMENT LXXVIII. 



Nicotine, Pilocarpine, Atropine. (Dog: Intraocular 



Nerves, Salivary Glands, Oxygen Consumption, Blood- 



pressure and Respiration.) 



(For the anatomy of the eye, see Experiment CXVII, 



page 394.) 



1. GiA^e a dog (10 kilos) a moderate or small dose of 

 chloretone and folloAv this with ether. Arrange to record 

 blood-pressure and respiration. Consult Fig. 281 and dis- 

 sect out the optic nerve in the right eye. (Consult Experi- 

 ment LXIII, 2). Study Fig. 281 carefully and dissect out 

 the orbit until the eye ball can be rolled around forAA^ard (in- 

 ward) enough to bring the trunk of the optic nerve into 

 vieAv. The skin around the outer canthus should be cut 

 aAYay and sometimes the bones of the orbit must also be 

 chipped out a little Avith bone forceps. Try to aA T oid dis- 

 turbing the blood A r essels entering the eye from behind. 

 When the nerve is isolated place the platinum electrodes 

 against the nerve sheath and, Avhile Avatching the pupil, 



