The causes which produce all these varieties of pulse, and the changes of the system which they indicate, are, upon the whole, pretty clearly explained by our author; and the reader who wishes to consult other abridgments of the doctrines of Galen, may find them in the works of Rhases, Haly Abbas, and Actuarius. We shall merely make a few more remarks upon some of the more obscure and least understood parts of the system. Respecting the myuri, Galen states that they all indicate a prostration of the vital powers, but differing in degree, according to circumstances. When the pulse gradually becomes smaller, and in like manner recovers its magnitude gradually, and so on alternately, so as to form the _recurrent myuri_, it indicates an inferior degree of prostration; and, when the diminished state of pulsation continues permanent, a greater degree of oppression is indicated. In the former case the powers of the system seem able to struggle against the load, but in the latter they are completely overcome. This state is next in danger to that of complete asphyxia. These three are the worst kinds of pulse. The _intermitting_ is said by him to be allied to these, being indicative of great danger, though inferior to that of those we have mentioned. Next to the intermitting is the _intercurrent_, which indicates that the powers of the system are strong, but oppressed, and contending against some great load. Galen was particularly apprehensive of the _intermitting_ pulse, which he held to indicate that the system is struggling against some urgent cause. He remarks, however, that, when the pulse is otherwise strong and frequent, it indicates less danger than when it is weak and slow. But, upon the whole, he considered this kind of pulse so full of danger, that he affirms he had never known a person recover whose pulse intermitted during the interval of two pulsations. When the pulse intermits during the space of only one pulsation or a little more, he says he had often seen the patient recover. He also states that an intermitting pulse is less dangerous in old persons than in adults or children. Some, he says, affirm that they have seen cases of intermission which did not prove dangerous, but he believes that they had confounded rarity with intermission. The intermitting is to be distinguished from the rare by the length of the time of rest, and by the latter being often equable, whereas the former is always unequable. He says it is generally occasioned by frigidity of the heart. These doctrines may be traced through all the subsequent authorities, both Greek and Arabian, down to Actuarius.