CAUSES OF EXOPHTHALMOS. 423 



discover what other nerves sippear to be irritated in exoph- 

 thahnic goitre, and consider what points exist at which applica- 

 tion of an irritant might affect all the nerves at once. 



Enlargement of the Thyroid Gland. — The great variations 

 v\diich occur in the size of the thyroid gland in exophthalmic 

 goitre, and its remarkable pulsation, which has sometimes 

 caused it to be mistaken for aneurism, have led nearly all 

 observers to ascribe its enlargement, in the first instance at 

 least, to dilatation of its vessels and engorgement of the gland 

 with blood, in a manner similar co that which occurs in erectile 

 tissues. After this has ?/>ntinued some time, increased growth 

 may occur in the glandular elements. This dilatation may 

 depend on direct paralysis of the vasomotor nerves of the 

 glandular vessels, or on inhibition of these nerves by others, in 

 the same way as tlie vaso-motor nerves of the penis cease to act 

 and allow the vessels to become full when the nervi erigentes 

 are irritated. The vasomotor nerves of the thyroid vessels 

 proceed from the second cervical ganglion, but I am not 

 acquainted with any experiment showing whether they pass 

 from the spinal cord to the ganglion through its communicating 

 branches, or pass upwards through the third cervical ganglion. 

 Neither do I know whether these vaso-motor nerves may be 

 inhibited, and the vessels dilated, by irritation of the third 

 cervical ganglion, or other parts of the nervous system. 



Froiriidou of the Eyeball. — In a case recorded by Laqueur* 

 the protrusion of the eyeballs seems to have been partly due to 

 an increased amount of fat within the orbit, but this may have 

 been only consequent on long-continued congestion. In many 

 cases the protrusion varies at different times, and in the case of 

 M. M. it is only temporary, disappearing in the intervals 

 between the fits. It is therefore usually ascribed, and in all 

 probability correctly, to increased fulness of the blood-vessels^ 

 or of the blood-vessels and lymphatics, in the orbit. It may be 

 also due, however, as suggested by Professor Laycock, to con- 

 traction of the involuntary muscular fibres stretching across 

 the back of the orbit, which were described by I'rofessor 

 Turner of Edinburgh some years ago. Whatever be the cause 



* Dissertation : Bei lie, 1861 ; Canstatt's Jahreshericht. 



