MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



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Flo. 47. Lower ends of hnmeri showing olecranon perforations. 



ordinarily separates the coronoid from the olecranon fossa of the humerus. The absorption of 

 this partition and the consequent formation of a perforation connecting the two fossae naturally 

 follows. 



Fig. 47 represents the anterior aspects of the distal extremities of both hurneri from the skele- 

 ton of a young subject in the Salado series. The right humerus has a single large olecrauon 

 opening. In the left humerus the partition be- 

 tween the two fossae is of a translucent thinness 

 and is perforated by a number of small orifices 

 which outline a space larger than the perforation 

 in the right humerus. This left humerus is be- 

 lieved to present an olecranon perforation in the 

 first stages of its formation. No other specimen 

 of this character has beeu seen by us. 



Our whole museum collection shows the per- 

 foration in two adolescents but in no infants. As 

 far as we can learn the same fact has been ob- 

 served with regard to children in other collec- 

 tions, and this is one of the facts on which rests 

 the theory that the perforation is acquired and 

 not inherited. 



If it be granted that the perforation arises 

 from mechanical causes and is the result of labor 

 which requires repeated and forcible extension of 

 the forearm, we need not search long to discover 

 the existence of such labor among the aborigines of the southwest, both ancient and modern. The 

 females of the modern pueblos are engaged during the greater part of their time in grinding corn, 

 and they begin to perform this labor while they are yet very young. The grinding is done on a 

 nictate or large flat stone, by means of a smaller stone which is held in the hands of the operator 

 and moved back and forth. The chief extension is made in moving the stone forward, and this 

 requires the most forcible extension of the forearm. The motion is made chiefly by the muscles 

 of the back. The discovery of numerous metates and upper grinding stones in the ruins of the 

 Salado cities shows that the people practiced a method of grinding similar to that of the modern 

 sedentary Indians of the same region. There were, no doubt, other labors which required great 

 extension of the forearm, but this we believe was the most important. 



Modern agricultural tribes of the North and East ground their corn in wooden mortars with 

 wooden pestles; and in so doing made motions very different to those employed in operating with 

 the metate. 



Pruuer Bey expresses the opinion that this peculiarity is, in the human race, to be found only 

 in females, because all the humeri in which he noted the perforation were small. We can not say, 

 for certain, that it is found only in female humeri, in the Salado series, because we can so rarely 

 determine the sex of these skeletons ; but it is not improbable that the perforation may be shown 

 to occur more frequently among the females than among the males. Although the men did much 

 hard labor of various kinds the work of grinding the corn was, in all probability, with the ancient 

 Saladoans, as with the modern pueblo Indians, performed exclusively by the women. 



That the perforation is not a peculiarity of females in all races is evidenced by the patholog- 

 ical series of the Army Medical Museum. In this series is a percentage of 7.9 perforations in 288 

 humeri, and these bones are, with few exceptions, derived from American soldiers of the Caucasian 

 race. It is easy to conceive that many of our modern mechanical employments, such as that of the 

 carpenter propelling the plane, in which the arm is forcibly extended, might cause the perforation 

 we speak of. We have in our anatomical series the skeleton of a Frenchman showing the perfo- 

 ration on one side. 



On the supposition that the perforation is produced by mechanical causes, we can account 

 for its preponderance on the left side only by supposing that the left arm, in many occupations, is 



