TRACHEAL RESPIRATION 



12: 



Wigglesworth (1929, 1930, 1931) has shown that any increase 

 in osmotic concentration has the effect anticipated. 



Fig. 69 shows the effect of hypertonic potassium lactate on 

 the air filling of tracheoles in an Aeschna larva. 



In the firefly (Photuris pennsylvanicus) and in the European 

 Lampyrida the tracheal system of the segments bearing the light 

 organs is independent of that of the rest of the body, and their 



Fig. 69. A, tracheal endings in mid-gut of Aeschna larva just after dissection, 

 B, after application of 3% potassium lactate. (Wigglesworth.) 



spiracles are kept closed during the daytime. The flashes of 

 light are initiated from the central nervous system, and Maluf 

 (Maleouf, 1938) has brought forward good evidence to show 

 that the mechanism is a sudden increase in osmotic pressure in 

 the light-producing cells, causing the absorption of tracheolar 

 fluid and an increased access of oxygen. Maluf finds that 

 injection of hypertonic substances produces a continuous glow. 

 A different conception of the mechanism regulating the 

 movement of tracheolar fluid was put forward quite recently 

 by T. Bult (1939) and supported by many experiments all 

 made on the same object, the isolated mid-gut of the cockroach 

 Phyllodromia germanica. According to Bult, the tracheole walls 

 are incompletely wetted by water and the effect of capillarity 

 therefore quite low. Evidence is presented to show that the 

 movements are caused by swelling of proteins within cells, 



