408 WORK OF THE PHYSIOLOGICAL .STATION AT PARIS. 



characteristics in tlie other pieces of the slicleton. Our .urcat natural- 

 ist could therefore, to repeat au expression that has become classical, 

 restore from a sinjile bone the entire skeleton of the animal to which 

 that bone belon,i;cd. 



Without the long- practice of a Cuvier, we may, by taking for our 

 guide aiiaitomico-physiological relations, arrive at determinations of a 

 simiUir kind which may seem astonishing to those who do not know 

 the theory by which they are reached. 



I have shown that it is sulhcient to see the wingi)f a bird, or even 

 the bones of the forearm of that wing, to deduce the dimensions of the 

 sternum.' These relations have not, as far as I am aware, been indi- 

 cated by anatomists. They are as follows: Birds with small wings 

 have the sternum long and narrow; those with the large wings have 

 that bone broad and short. This relation is easy to verify on the skele- 

 tons of birds in zoological collections. The considerations wdiich led 

 me to predict this are as follows : 



In w^atching the flight of birds it is seen that large-winged species 

 have wing beats of but slight extent. This is because the large sur- 

 face of their wings finds a strong resistance in the air. Species that 

 have but little wing surface have, on the contrary, wing beats of great 

 amplitude in order by motor work and by the length of the i^ath 

 described to make amends for the feeble resistance. Having .such dis- 

 similar movements, these two kinds of birds ought to have correspond- 

 ing differences in the great pectoral muscles that lower the wings. In 

 the first these muscles are large and short; in the second, long and 

 slender. But the sternum, in the lateral fossa^ of which these muscles 

 are inserted, must correspond in its form to that of the muscles them- 

 selves. It must therefore be broad and short in the first type of birds, 

 long and narrow in the second. All sorts of intermediate forms exist 

 between these two extremes. 



A comparison of the skeletons of birds shows that it is really so. 

 Still, gallinaceous birds seem to offer an exception to the rule; they 

 have a sternum too short for the small surface of their wings. But in 

 these species the great length of the coracoid bones really prolongs the 

 sternum, so that the exception to the general rule is only apparent. 



The same kind of relations led me to predict, from the conformation 

 of the muscles of the calf, a curious i)eculiarity of the skeleton of the 

 negro. Comparing the calves of the negro with those of the white man 

 it is seen that in the first the gastrocnemii are much longer and more 

 slender, which allows us to conclude that the muscles have less force 

 but more range of motion in the black race. Now, to get tlie same 

 results of work expended in walking, it is necessary that the muscles 

 should act upon a longer lever; or, to state it otherwise, that the dis- 

 tance should be greater between the end of the calcaneum and the center 

 of movement in the ankle joint. Measurements show that this predic- 



' La Mackiue Auimale, Chapter VIII. 



