LIVING PRINCIPLE. 117 



is another principle [or cause] is evident and demonstrable ; this is the 

 blood. But whether this fluid is immediately concerned, or is a re- 

 mote cause acting upon the nerves, may not, perhaps, be easily deter- 

 mined. 



Let us now trace this cause by comparing the bloods in [the above] 

 different [classes of] animals, and see if, where the blood is similar in 

 any two dissimilar animals, the principle above mentioned be similar ; 

 and, if so, in what respect the two bloods are similar to produce this 

 similar effect. In the first class [Tetracoilia~] the motion of the blood 

 is extremely [rapid and the blood is] perfect ; and this perfection de- 

 pends upon the single circumstance of its having been thoroughly ex- 

 posed to the external air by means of the lungs ; so that none of this 

 kind of blood goes to the body but what is truly pulmonary [in the 

 sense of having circulated through the lungs]. In the second class 

 [Tricoilia] the blood has not this advantage ; the construction of the 

 parts upon which the motion of the blood depends will not admit of it : 

 and we find the blood passing to the different parts of the body very 

 imperfect in this respect. It is composed of a mixture of pulmonary 

 [i. e. arterial] and venal. So far these two [classes of animals] are not 

 similar ; and we observed that they were not similar in the affair of the 

 continuance of Simple Life, when deprived of the sensitive, and of the 

 motion of the blood. So it would seem from this view, that the 

 greater power of Simple Life in the one over the other was owing to 

 an imperfection in the blood ; but, most probably, this is not the case, 

 as will be mentioned hereafter. 



Let us see how far the third class \Dicoilia] will throw light upon 

 this subject. The mackerel and the eel are exactly of the same con- 

 struction as far as relates to the motion of the blood ; therefore, from 

 the mere construction of the parts upon which the blood's motion de- 

 pends, no argument can be brought to bear. We find that a mackerel 

 loses the Simple Life immediately, whether it be deprived of the blood's 

 motion, or be deprived of perfect pulmonary blood ; either of these causes 

 having the same effect. The eel retains the Simple Life for a consi- 

 derable time when, either deprived of the blood's motion, or when de- 

 prived of the perfect pulmonary blood. Hence we might conclude that 

 this principle of Simple Life does not require perfect blood, and there- 

 fore will exist a considerable time without blood at all. And it will 

 follow, that an animal which has a superabundance of this principle, 

 will have, in the same proportion, less need of a perfect blood or even 

 blood at all, and will retain the principle of simple life a much longer 

 time than those who have less of it and more of the sensitive life. 



Do animals which are easily killed sooner putrefy than those that 



