128 Thomson^ s Lectures on Botanij. 



order." This is only noticed in passing, to show the lecturer's opinion of 

 Jussieu's system in 1822. 



The next branch of the lecture is on the utility of botany. Here is noticed 

 the abandonment of vegetable qualities by the medical empiric Paracelsus, 

 in favour of chemical qualities drawn from the mineral kingdom ; and, though 

 the last are duly appreciated, Dr. Thomson thinks the change in so far unfor- 

 tunate,as it has withdrawn the attention of the physician too much from the 

 study and analysis of vegetable remedies : he regrets this the more, because 

 plants are naturally classed by their predominating qualities; a;,theCruciferae 

 are salutary ; the Jpocyneae, suspicious; and the Umbelliferae, deleterious; 

 and also vary in quality, according to their habitat being moist or dry, 

 calcareous, or arenaceous; a knowledge of such circumstances being always 

 useful to the medical practitioner, as thence may arise discoveries valuable to 

 his country and to the human race. Some pertinent observations are added, 

 on the necessity of the medical staff of an army being capable of identifying 

 the i)lants round the camp, as affecting or not the health of the soldier ; 

 adding, that " the very plants which cover the soil, clothe with a prophetic 

 character the botanical physician, and enable him to anticipate the danger 

 which it is requisite to avoid." He gives the names of several eminent 

 physicians who were also botanists ; and shows not only what has been 

 added to the materia medica by such men, but also the extreme danger of 

 a physician being ignorant of vegetable toxicology. 



From these observations on the necessity of botany being a part of medi- 

 cal education, he adverts to its being also necessary for the farmer, which, 

 united with some knowledge of chemistry, would invest him with new powers 

 in the successful prosecution of his important occupation. On the advan- 

 tage of botany improving the mind, the lecturer has the following remark: 

 " Many branches of knowledge have this effect; and, although they cannot 

 be considered as directly advancing our interests or our fortune in our 

 intercourse with mankind, yet the possession of them affords a more per- 

 manent satisfaction than either wealth or honour can bestow." 

 ; On the mode of studying botany he observes, that vegetables, like ani- 

 mals, are organised living bodies ; and, though there is no difficulty in 

 distinguishing them from animals and fossils, yet the line of distinction is, 

 in some instances, hardly perceivable ; that plants are perishable, draw 

 nourishment from the soil, and are capable of reproduction; that they possess 

 irritability, by which the nutriment they imbibe is moved through every part 

 of their bodies, converted into various secretions (separations),and assimilated 

 (converted to the same nature) into the substance of the plant itself; but 

 they have no sensibility, though even this has been attributed to them by 

 some writers. That part of the subject, therefore, which refers to the 

 vegetable system, should first engage the attention of the student. It con- 

 stitutes phytology, and comprehends the anatomy and physiology of plants. 

 The anatomy of plants is more difficult than that of animals, but less dis- 

 gusting ; and, without the microscope, we can have no idea of the structure 

 of plants, and consequently no correct notions of their functions can be 

 obtained : but, by combining with anatomy and terminology (proper terms), 

 the study of physiology, on which modern chemistry has thrown the most 

 brilliant light, the tediousness of acquiring the terms of art is diminished, 

 and much interest excited in the pursuit. 



To obtain all this, the lecturer recommends the works of Smith, Rous- 

 seau, Curtis, Willdenow, Mirbell, Sims, Keith, &c. The respective merits of 

 these writers are noticed in the course of the lectures ; and Jussieu's system, 

 which now divides the botanical world, he again mentions without com- 

 mendation ; alleging, as his reason, that " in the present state of our know- 

 ledge, a natural system cannot be formed." 



Lecture 2. — Definition of a Plant ; General View of vegetable Func- 

 tions. This commences by noticing the three grand divisions of natui'e, viz. 



