58 



RESPIRATORY MECHANISMS 



strated the absence of cutaneous respiration. Hazelhoff (1926) 

 showed on a number of spiders, and Fraenkel on a scorpion 



Fig. 33. Abdomen with tracheae of Heliophanes cupreus. (Lamy.) 



(Buthus), that the spiracles remain almost closed when the 

 animal is at rest and the temperature not too high, thereby 



