Dunglison's Human Physiology. 167 



measure, from embarrassing circumstances of this kind, might be 

 formed, by the united labor of learning, talent and industry, upon 

 something like the following plan. 



Many of the leading and most important doctrines in physiolo- 

 gy, are firmly established, and are universally received as funda- 

 mental truths ; such as the circulation of the blood, the sensibility, 

 both common and peculiar, of the nerves, the power of alternate con- 

 traction and relaxation of the muscular fibre, and numerous others 

 of a similar character. These should be fully and distinctly stated 

 as established principles, and should be accompanied by the facts by 

 which they are proved. There are many others, such as the doc- 

 trine of the vitality of the blood, the contractile power of the middle 

 tunic of the arteries, the agency of a peculiar fluid in the stomach 

 in the process of digestion, &,c. which, although rendered highly 

 probable by a multitude of supporting facts, are yet with difficulty 

 reconcilable to others, and are therefore not universally received. 

 These should be laid down, as a distinct class of principles ; all the 

 facts bearing upon them should be fully detailed, their truth or fallacy 

 fairly canvassed, and whatever the opinion of the author concerning 

 them may be, an impression should be left upon the mind of the 

 reader, that, in the present state of the science, they are still unset- 

 tled, and therefore open for further investigation. Besides these, 

 there is another large class of opinions, often the result of highly in- 

 genious speculation, which yet are too slightly in accordance with 

 known facts to challenge belief, and which still ought not to be passed 

 over. These consist, for the greater part, of attempted explanations 

 of the hitherto unintelligible processes of several parts of the animal 

 body; such as speculations concerning the functions of the spleen, 

 the lymphatic glands, ganglions of the nerves, &:c. Such of these 

 opinions as deserve notice at all, either from their ingenuity, or their 

 semblance to truth, should be stated both to show the train of thought 

 upon these subjects in which ingenious minds run, and as a connect- 

 ing medium of all the known facts in relation to them. 



The object of this plan is to place distinctly and severally before the 

 mind of the inquirer into the doctrines of physiology, all that is known, 

 all that is believed and all, of importance, that is conjectured concerning 

 them, giving to each class its due weight and bearing. In this way much 

 labor and perplexity would be saved to those who are entering upon 

 the study of this important science. The great difficulty in execu- 

 ting a work upon this plan, in addition to the learning and talent which 



