PERCEPTIONAL INSANITIES. 765 



The causes of central illusions and hallucinations are generally to 

 he found in derangements of some kind in the blood circulating in the 

 brain. These may either relate to its quantity or its quality. 



Physical influences calculated to produce cerebral hypersemia or 

 congestion may give rise to illusions or hallucinations. Brierre de 

 Boismont refers to a case, on the authority of Moreau, in which an 

 individual was able to obtain hallucinations of sight by inclining his 

 head a little forward. A similar case was not long since under my 

 own care. A gentleman, while sitting at his table writing, happened 

 to raise his eyes without moving his head, and saw before him the 

 figure of an old woman with black cloak and hood. Throwing him- 

 self back in his chair in his amazement, he found that the image slowly 

 disappeared ; and, as often as he repeated these movements, a like 

 series of phenomena occurred. On examining him, I found that he 

 wore a very high, old-fashioned stock, which, as he sat at the table 

 with his head bent forward, compressed the large veins of the neck, 

 and prevented for a time the return of blood from the brain. On 

 chanffimx his neck-wear for other of more modern fashion, he was ena- 

 bled to bend his head and raise his eyes without encountering the ap- 

 parition. 



A gentleman once consulted me who, for several weeks, had seen, 

 just as he lay down, the figure of a very old man, who stood by the 

 side of his bed grinning and beckoning to him. At first he was de- 

 ceived, and started suddenly from his bed, whereupon his visitor dis- 

 appeared. He marie several tests which satisfied him as to the real 

 character of the phantom, and then, like a sensible man, tried to get 

 to sleep, but in this attempt he succeeded badly. 



The explanation of such cases is very simple. The recumbent pos- 

 ture facilitates the flow of blood to the brain, and at the same time 

 tends, in a measure, to retard its exit. Hence the appearances were 

 due to the resulting congestion. As soon as the individual rose in 

 bed, or stood erect, the reverse conditions existed, the congestion dis- 

 appeared, and the apparition went with it. 



The influence of cerebral hyperozmia in causing hallucinations seems 

 to be clearly established. Ferriar wrote a treatise with the special ob- 

 ject of proving that this is the only cause. This is an extreme view, 

 however, which can not be sustained, for that the very opposite con- 

 dition, cerebral anaemia, is an immediate cause of hallucinations is seen 

 in the facts that, during starvation and other conditions producing 

 great bodily exhaustion, hallucinations are common occurrences. 



A striking instance has recently come under my observation, which 

 shows, undoubtedly, that a reduction in the amount of blood circu- 

 lating within the cranium may give rise to hallucinations. A young 

 woman affected with epilepsy had repeated seizures while in my con- 

 sulting-room, and, with a view of arresting them, I exerted strong 

 pressure on both carotid arteries. Her face instantly became pale, 



