TRANSACTIONS OF THE SECTIONS. 103 



The course of the trunks of arteries (with two or three exceptions,) 

 is as much in straight lines from one part to another as that of the nerves, 

 when the vessels are not displaced by dissection and forcible injection. 



The position of the three facial nerves, where they emerge from their 

 foramina, is almost with perfect exactness upon vertical lines, which 

 would divide a well-proportioned face into thirds ; but for the purpose 

 of fixing the points at which these nerves may be divided, the author 

 has laid down the following rules : a vertical line, drawn so as to pass 

 midway between the external angle of the orbit and the middle line of 

 the forehead, will cover the supra-orbital nerve as it escapes from the 

 notch or foramen, as the case may be, on the superciliary ridge. For the 

 infra-orbital nerve, the following lines may be drawn : 1st, one perpen- 

 dicular along the outer side of the second bicuspid tooth ; this will 

 divide the orbit in the middle. 2nd. A line from the external angular 

 process of the orbit to between the two middle incisors of the upper 

 jaw ; this line covers the course of the nerve as it comes out of its 

 foramen. 3rd. A line may be taken from the lower part of the inter- 

 nal angular process of the osfrontis to the angle of the lower jaw ; this 

 line passes across the nerve a few lines beyond its exit from the infra- 

 orbital hole, and indicates the direction in which the nerve should be 

 cut. 4;th. If two lines be drawn, one from the internal, the other from 

 the external angular process, so as to meet and form an equilateral tri- 

 angle with the horizontal line from the same points, the inferior an- 

 gle will determine the distance of the foramen from the inferior margin 

 of the orbit. By the intersection of these lines and their direction, the 

 most perfect knowledge may be obtained of the position of the infra- 

 orbital nerve for the purpose of its division. 



The mental nerve, immediately on the outer side of its foramen, is 

 crossed by a line dropped vertically from the superciliary notch. The 

 height of this nerve on the jaw will vary according as age may have 

 changed the form of the bone ; but this is of no importance, as the di- 

 vision of the nerve is best effected on the inside of the mouth, which 

 produces no deformity. 



Dr. Macartney further observes, that the same primary relations re- 

 gulate all the progressive, and many other movements of all animals 

 provided with extremities. They also constitute the foundation of the 

 measure in music, and the rhythm of language. All musical time con- 

 sists essentially of divisions or bars, containing two or three notes, or 

 multiples of these numbers, and in no other proportions are we able to 

 count it. Our powers of perception even are subjected to the same 

 law of proportion. If we attempt to look at more than two or three 

 objects at the same moment, and without shifting the attention from 

 one to the other, we find that it is impossible to distinguish or compare 

 their differences except by making parcels of them, and then each of 

 these aggregations represents an unit. The author adds, that the com- 

 binations of doubles and thirds produce the proportions in all archi- 

 tectural forms, which yield us the most pleasure to contemplate. 



Dr. Macartney began his observations on this subject as early as 

 the year 1798, and has now had forty-one years' experience of the 



