Such is our view of the etiology of manic-depressive insanity as a whole. When we approach the study of benign stupors, however, difficult problems appear. As will be discussed in a later chapter on the literature, reactions resembling benign stupors occur as a result of toxins, particularly following acute rheumatism. Recently the medical profession has been called on to treat many cases of encephalitis lethargica where similar symptoms are observed. If the resemblance amounted to identity, we would have to admit that a specific toxin may produce a specific mental reaction which we have concluded on other grounds to be psychogenic. As a matter of fact, in two particulars these reactions show relationship to organic delirium. Knauer reports that in post-rheumatic stupors illusions are frequent--an ice bag thought to be a cannon, or a child, etc.--and there are bizarre misinterpretations of the physical condition, such as lying on glass splinters, animals crawling on the body, and so on. Such illusions are, in our experience, not found in stupor, and, on the other hand, are cardinal symptoms of delirium. Further, Knauer reports that even at the height of post-rheumatic stupor, external stimuli make some impression, in that a thoughtful facial expression appears. In deep stupors, such as occurred in our series, this response is not seen. The same phenomenon of “rousing,” larval in Knauer’s cases, is often well marked in encephalitis lethargica and is, of course, a pathognomonic symptom of delirium. We might therefore think that these conditions are mixtures of two organic tendencies, namely, delirium and coma. It is not impossible that resemblances to benign stupor are due to functional elements appearing in the reduced physical state as additions to the organic symptoms. The prominence of pain might be taken as a likely cause for an instinctive reaction of withdrawal, which would account for the emotional palsy of these conditions on psychogenic grounds. [This argument can be better understood when the chapter on Psychological Explanation of Stupor has been read.] We therefore feel justified in holding that the resemblance of the symptoms of certain plainly organic reactions to those of benign stupor do not necessitate a splitting of these stupors from the manic-depressive group.