_Affection._ The affections should be tested in an indirect way. "Is your father a bad man?" or "Are your neighbours worthless people? Do they treat you with due respect? Has any one a spite against you? Are you fond of your parents? Are you aware that your brother (or mother) is seriously ill?" Questions concerning relatives and friends are of special interest, because they enable the examiner to ascertain whether they cause the patient emotion of any kind, whether he has any real affection for those beings to whom normal persons are attached, but towards whom born criminals and the insane in general do not manifest love. In the absence of instruments, we must judge of the feelings of patients by their answers and the facial changes caused by emotion, but medico-legal experts naturally prefer a scientific test by means of accurate instruments, by which the exact degree of emotion is registered. These instruments are the plethysmograph and the hydrosphygmograph.
It is well known that any emotion which causes the heart-beats to quicken or become slower makes us blush or turn pale, and these vaso-motor phenomena are entirely beyond our control. If we plunge one of our hands into the volumetric tank invented by Francis Frank, the level of the liquid registered on the tube above will rise and fall at every pulsation, and besides these regular fluctuations, variations may be observed which correspond to every stimulation of the senses, every thought and above all, every emotion. The volumetric glove invented by Patrizi (see Fig. 25), an improvement on the above-mentioned instrument, is a still more practical and convenient apparatus. It consists of a large gutta-percha glove, which is put on the hand and hermetically sealed at the wrist by a mixture of mastic and vaseline. The glove is filled with air as the tank was with water. The greater or smaller pressure exercised on the air by the pulsations of blood in the veins of the hands reacts on the aerial column of an india-rubber tube, and this in its turn on Marey's tympanum (a small chamber half metal and half gutta-percha). This chamber supports a lever carrying an indicator, which rises and falls with the greater or slighter flow of blood in the hand. This lever registers the oscillations on a moving cylinder covered with smoked paper. If after talking to the patient on indifferent subjects, the examiner suddenly mentions persons, friends, or relatives, who interest him and cause him a certain amount of emotion, the curve registered on the revolving cylinder suddenly drops and rises rapidly, thus proving that he possesses natural affections. If, on the other hand, when alluding to relatives and their illnesses, or vice-versa, no corresponding movement is registered on the cylinder, it may be assumed that the patient does not possess much affection.