118 



IOWA ACADEMY OF SCIENCES. 



Fourth. The blood does not ordinarily enter each root by means of a 

 single apical foramen as commonly taught. On the contrary there are 

 usually several, sometimes more than a dozen such foramina in a single 

 molar root after the animal has reached maturity. 



The above statements indicate such a radical change of view regarding 

 the vascular supply of the teeth that something more satisfactory than mere 

 assertions will doubtless be expected. In order to meet this reasonable 

 expectation the illustrations accompanying this account have been prepared 

 with considerable care. The sections from which the drawings are taken 

 ai-e injected and not decalcified, and were prepared by the writer, who still 

 has them in possession. It will be understood that the views here advanced 

 are based on numerous dissections and sections besides those illustrated by 

 the drawings. 



It was found that drawings were more available than photographs, for 

 the reason that the thickness of the sections and the irregularity of the 

 vessels required a depth of focus which could not be secured by use of the 

 camera. Although all drawings are uecessai-ily interpretations of the artists 

 views, it is hoped that there is nothing misleading in the illustrations here- 

 with presented. They may be considered correct in so far as they do not 

 represent a single vessel pursuing a course not found in the sections exam- 

 ined. 



In conclusion, your attention is called to the fact that this matter has a 

 practical bearing. The teeth of the Carnivora, as Owen says, so closely 

 correspond in their intricate structure both with each other and with those 

 of the " Quadrumana " as not to require separate discussion. More than 

 this it is highly improbable that there should be any essential difference 

 between the teeth of the cat and those of man in the method of furnishing 

 blood to this important structure. 



Dr. A. O. Hunt, dean of the dental faculty of the State University, says 

 that the excessive hemorrhage sometimes attending extraction of the teeth 

 is due to the breaking of the septum between the teeth, which, as my sec- 

 tions show, contains large branches of the dental arteries. If these arteries 

 penetrated directly to the pulp through the root excessive hemorrhage 

 would always result from the pulling of the tooth. It makes a vast prac- 

 tical difference whether a multitude of minute vessels or one large vessel is 

 broken. In the former case, little hemorrhage would result, while in the 

 latter it would be a serious matter. These sections are necessarily thick, 

 as thin sections would fail to show the continuity of the vessels, a vital 

 point in the investigations upon which this paper is based. The sections, 

 although quite thick, were rendered sufficiently translucent by long immer- 

 sion in benzole, after which they were mounted in Canada balsam. 



