4 28 



ELEMENTARY ANATOMY. 



[LKSS. 



(Fig's. 356 and 362) and a sinus venosus, forming as it were 

 two supplementary cavities to the heart. Even in man's own 

 class, parts so remote from the heart as the veins adjacent 

 to the ringers may become rhythmically contractile under 

 special circumstances, as we have seen with regard to the 

 Bat's wing. 



The connexion between the systemic and pulmonary 

 circulation takes place in all higher Vertebrates, as in man, 

 i.e. only in the heart its confusion in lower forms has just 

 been mentioned. 



The connexion between the blood carried to the gills and 

 that which finds its way to the dorsal aorta may, as in most 

 Fishes (e.g. the Perch), take place only by the capillaries of 



FIG. 368. INFERO-LATERAL VIEW OF HEAD AND AORTIC ARCHES 

 OF LEPIDOSIRHN. 



(After Hyrtl.) 



a, oesophagus ; b, anterior end of bulbus aortse ; c, common roots of the first aortic 

 arches ; d, third aortic arch ; e, first aortic arch ;f, dorsal union of the three 

 first aortic arches ; g, aorta; k, caeliac artery; z, exit of the fifth nerve ; k, 

 part of operculum ; /, exit of the nervus vagus from the skull ; m, branches to 

 oesophagus ; n, nerve going to the rectus abdominis ; <?, nervus lateralis ; p, 

 first and hypertrophied rib ; q, posterior part of skull ; r, segmented neural 

 spines; s, chorda dorsalis ; t, mandible; n, quadrate. 



the gills. 1 But, on the contrary, the vessels taking the 

 blood from the heart to the gills may be connected by 



1 For details of the circulation in the gills see p. 479, Fig. 405. 



