When it is warm, or when we are feverish, and the blood tends to flow more abundantly to the surface of the body to cool itself, the secretion of perspiration is increased in a similar way. But we see anæmic persons perspire--the consumptive, for instance, and the dying, in whom this more copious supply of blood is wanting. In this case the cause of abundant secretion is different; here it is the nerves. One of the finest discoveries which have been made of late years in physiology, is that of the nerve-filaments which connect the cerebro-spinal system with the glands of the body. Whereas formerly everything was attributed to the more or less copious flow of blood to the glands, the secretions of which were considered as a process of filtration, we now know that the matter is much more complicated, and that there are nerves which augment and diminish the activity of the cells charged with the secretion. It is nervous activity which produces the perspiration characteristic of attention, pain, epilepsy, tetanus. In order to prove that the secretion of perspiration may be accomplished independently of the circulation of the blood, we make an incision in the leg of a cat immediately after death and irritate the sciatic nerve; we then see that a secretion of perspiration still appears on the sole of the foot. From this we can understand how in the death-agony and the extreme pallor of fright, when all the vessels of the skin are contracted, there yet may appear a peculiar secretion of perspiration which we call _cold perspiration_. IV There is another part of the body which opens periodically to allow of the ejection of the refuse of the factory; it consists in a _cloaca_ and a cistern which contains a yellow liquid. It is a less beautiful part of the organism, but during violent emotions involuntary movements are produced in it so characteristic of fear that we must turn our attention to it. Physicians thought that these irregularities were caused by a paralysis of the sphincter muscle, but this is not the case. The researches which I made with Prof. Pellicani[26] showed that, in man as well as in animals, there are strong contractions of the bladder which correspond to psychic facts. Scarcely have we experienced some slight emotion or been excited by some thought but there is an immediate change in the state of the muscles of this organ. I regret that the nature of this book does not permit of the reproduction of the curves traced by the plethysmograph, which show that psychic phenomena and any irritation of the sensory nerves produce a contraction of the bladder. [26] Mosso e Pellicani: _Sulle funzioni della vescica_. R. Accademia dei Lincei, vol. xii. 1881.