Nov. 15, 1911 



689 



Fig. 6.— a fiber of fascicle muscle: t, trachea. 



of development. Their structure is similar 

 to the texture of the striate muscles of the 

 vertebrates. One may discern a well-distin- 

 guished longitudinal striation and trans- 

 verse striation not less characteristic. The 

 longitudinal striation is due to the great 

 number of fine fibrils, forming a fascicle. 

 The transverse striation owes its origin to 

 the fact that each fibril is composed of 

 sheaves of more or less refraction. P'ig. 7 

 shows, in a transverse section, the fibers. 

 A few nuclei are scattered rather regu- 

 larly between the fibrils, which are not 

 clearly shown in Fig. 6, but visible in Fig. 

 7. There is no sarcolemm around the fasci- 

 cle, but a multitude of tracheae penetrate 

 between the fascicles. For example, see 

 Fig. 8, showing a transverse section of the 

 breast of a drone. Fig. 9 shows a great mag- 

 nifying of these tracheae, whose walls are 

 strengthened by minute chitinous rods.??o^ 

 From those tracheal branches emerge a 



Fig. 8.— Transverse section of drone breast: 1, leva- 

 tor of wing: d, depressor of wing; b,?basis of wing; 

 oe, oesophagus: g. ganglion. 



great number of extremely fine air-tubes, 

 like little trees, sending their boughs into 

 the interior of the fascicles. In Figs. 8 and 

 9 only the chitinous rods are impregnated 

 with silver by a special method of coloring. 

 As the finest air-tubes do not contain any 

 of those chitinous rods, nothing is seen of 

 them in the photos. If they too had been 

 colored the figure would show nothing but 

 a thick web of black lines. The exchange 

 of oxygen and carbonic acid takes place only 

 in those minute air-tubes. 



The exceedingly rich supply of the flight 

 muscles with tracheae proves the great im- 

 portance of the gas exchange in the muscles. 

 Indeed, the task of the flight muscles is 

 enormous, the flight of a body heavier than 

 air requiring great mechanical labor. De- 

 liberating on the quickness of the movement 

 of the four wings, one may conceive that 

 the rather simple-structured tube muscles 

 can not suffice, and that here organs are re- 

 quired which possess a considerably higher 

 development. 



The breast contains three jiairs of air-en- 

 trances (stigmata) , and the respiration must 

 take place in such a manner that the alter- 



W Fig. 7.— Transverse section of a fiber of the fascicle 

 muscle: n. nuclei. __^ 



FIG. 9.— Tracheee in a fasicle mviscle. 



