OF THE ACALEPHiE OF NORTH AMERICA. 327 



filled with a large quantity of blood, and appear intensely red, after some violent motion. 

 It might be objected, that this is a mere influence of locomotion upon circulation ; but 

 if there were not this natural disposition in all locomotion to influence the process of 

 respiration more than any other system, why should not the blood, when such powerful 

 motions take place, be accumulated in any other part of the body, — for instance, in the 

 tail, which is the very cause of the motion, — rather than in the gills? In birds the 

 extensive development of the lungs, the prolongation of air-sacs into the abdominal 

 cavity, the wings, and the sternum, in those most, remarkable for their power of flight, 

 plainly indicate again the most strict connection between locomotion and respiration, 

 though the nature of this connection be perhaps different from that which is observed 

 in the lower classes. Nevertheless, it exists and can be traced to a very remarkable 

 extent. We cannot fail to trace, also, similar relations among Mammalia, though here 

 the influence between the two functions is not so direct. However, it" must be 

 acknowledged that it is extensive enough, when we consider how the aquatic types 

 have to accommodate all their movements to the wants of the system for atmospheric 

 air, and remain constantly within reach of the surface, in order to be able to return to it 

 in a short time. How^ much the breathing is affected by violent movements is so well 

 known to every one, that the existence of accessory muscles of respiration in Mammalia, 

 the antagonism between the pectoral and abdominal muscles and the diaphragm, the 

 use of belts by athletes in running, leaping, or wrestling, need hardly to be further 

 mentioned as evidence of this mutual relation. Of course, in animals in which all the 

 functions have reached a great degree of independence, they are no longer subservient 

 to each other to such a degree as they were in the lower types ; but even the unpleasant 

 influence which excessive exercise of the locomotive power has upon respiration in the 

 higher animals shows the intimate relation which prevails in the plan of organization. 



One peculiarity which might be mentioned as indicating a further connection between 

 locomotion and respiration, if the vertical rows of locomotive fringes are at all con- 

 nected with respiration, is the circumstance that they serve, for their whole extent, as 

 points of attachment for the muscular system, as we shall see presently when describing 

 the contractile tissue. This connection, also, may remind us of the connection which 

 exists in Vertebrata between the anterior limbs and the chest. 



When examining; the structure of the vertical rows of locomotive fringes, we 

 encounter considerable difficulties, to which I would call special attention, for the 

 benefit of those who may have an opportunity to repeat these investigations. The 

 best way to study their peculiar structure is to cut off from the body a portion of 

 the row, say three or four transverse combs, and to bring them separately under the 



