Chap, iv.] THE ORBIT AND EYE. 33 



interval between the closing of the two vessels was 

 less than a few weeks. The vertebral arteries can 

 carry a sufficient amount of blood to the brain if only 

 the strain be thrown upon them gradually, and the 

 brain be allowed to accommodate itself slowly to the 

 change. Plugging of any of the smaller cerebral 

 arteries by emboli, as a rule, leads at once to a marked 

 disastrous result. Such embolism is met with in 

 surgery in connection with aneurism of the common 

 carotid. In simply examining such aneurisms, a 

 little piece of the clot contained in the sac has been 

 detached, has been carried up into the brain, and has 

 produced a plugging of one of the cerebral vessels. 

 Thus, hemiplegia has followed upon the mere exami- 

 nation of a carotid aneurism, as in a case recorded by 

 Mr. Teale, of Leeds. Fergusson's treatment of 

 aneurism at the root of the neck, by displacing the 

 clots by manipulation, has been abandoned on this 

 same score. In the second case treated by manipula- 

 tion by this surgeon, a case of subclavian aneurism, 

 paralysis of the left side of the body followed at once 

 upon the first handling of the tumour. 



CHAPTER IV. 



THE ORBIT AND EYE. 



THE orbit. The antero-posterior diameter of il ^ 

 orbit is about 1| inches, its vertical diameter at the 

 base a little over 1|- inches, and its horizontal diameter 

 at the base about 1J inches. The diameters of the 

 globe are as follows : transverse, 1 inch ; vertical and 

 antero-posterior, both O96 of an inch. The eye- 

 ball is therefore nearer to the upper and lower 



D 



