Up to this point we have discussed the various troubles subsumed under the term shell-shock in what may be termed its initial and middle stages. In the middle stage, the patient having recovered from the severe and acute symptoms constituting the former phase, is left with a motley residuum of troubles, the chief of which we have enumerated on pages 12, 13. In distinguishing between this middle stage and that which follows it, we may perhaps ask the reader to assist us by recalling the difference between a mechanical mixture and a chemical compound. In the former the ingredients of the mixture remain unaltered and unaffected by the proximity of other substances, as for example when sugar is mixed with sand. In the compound, on the other hand, chemical action and reaction occur between the components so that not one of the substances is immediately recognisable in the complex, as for example when carbon, hydrogen and oxygen combine to form alcohol, which resembles none of them. Now it would be distorting the facts of mind to suggest that while the third stage of shell-shock is a compound (as it undoubtedly is) the middle stage is a mixture. For the very essence of mind is its compound nature. But what we wish to point out is that in this middle stage the abnormalities have had very little time to react upon each other, with the result that there is some resemblance to a state of mixture, the phenomena existing temporarily side by side, so to speak. In this stage a patient may be troubled simultaneously by several unusual mental occurrences, such as terrifying dreams during very light sleep, loss of memory for certain periods of his past, and inability to understand or to carry out complex orders. For a short time in his “bowled-over” state he may be worried by the separate attacks, of these various troubles at different periods of the day and he may be too overwhelmed to try to understand or to attempt to see relations between them. This state of mind, in which the patient is still his “old self,” though a somewhat overturned self, resembles the mechanical mixture in our illustration. The reader may obtain some idea of this condition if he recalls any one day in his own experience when “everything seemed to go wrong”; when at one moment he was turning to face this difficulty, at another, that, but still retained to a great extent his usual attitude towards the world.