THE HEART AND ITS OSTIA 



399 



like the first, is directed forwards into the chamber. It is between these two 



valves on each side that the blood passes into the heart, and is prevented from 



returning by the closing of the semilunar 



valve. When the blood is passing into the 



chamber, the interventricular valve is 



thrown back against the side of the cavity, 



but is closed when, by the contraction of 



the transverse fibres, the diameter of each 



chamber is narrowed, and the blood is 



forced along into the next chamber." 



(Newport.) 



According to Miiller, there is but a single 

 pair of ostia in Phasma, and, in the larva 

 of Corethra, the heart is a simple, unjoin ted 

 tube, not divided into chambers, and Vial- 

 lanes states that, in the very young larva 

 of Musca, there are no ostia (Kolbe). In 

 the larva of Ptychoptera, Grobben found a 

 short oval heart, with one pair of ostia 

 situated in the 6th abdominal segment ; a 

 long aorta proceeds from it, the thoracic 

 portion of which pulsates ; from behind 

 .r-C*r~^ the heart arises a pul- 



/ ! \ \ sating pouch, which con- 



nects with the hinder 



aorta, which does not 



pulsate, and ends at the 



base of two tracheal 



gills. Burmeister was 



able to find only four 



pairs of openings in the 



larva of Calosoma. 



Newport states that, 



while Straus figures 



nine chambers in Me- 



lolontha, and, conse- 

 quently, eight pairs of 



openings, he 



been able 



more than 



has not 

 to observe 

 seven pairs 



of openings in Lncanus 

 cervus. He has invari- 

 ably found eight pairs 

 of openings both in the 

 larva and imago of 

 Sphinx Hf/ustri, as well 

 as in other Lepidoptera. 

 According to Be'la-Dez- 

 so, the number of pairs 

 of ostia corresponds to 

 that of the pairs of stigmata. 



There also occur, on each side of each chamber, two so-called pear-shaped 

 bodies which are separated from the tubular portion of the heart itself, but, by 



FIG. 372. Heart of 

 Belostoma. After 

 Locv. 



FIG. 371. ^4, heart of Lucanus cer- 

 vus : a, valves or chambers ; bb, alary 

 muscles : c, supposed auricular space 

 around the heart. , division into arter- 

 ies of the end of the aorta in larva of Ya- 

 nenfi/1 iirfii'ie. < ', interior of the chamber, 

 showing- the transverse fibres ; li, auriculo- 

 ventricular opening and valve into the 

 chambers; c, semilunar valve; <l, inter- 

 ventricular valve. After Straus-Diirck- 

 heim, from Newport. 



