We are about to discuss a subject as critical and important to take up as the abdominal aorta; for should we offend the class we are about to portray, there are fifteen hundred medical students, arrived this week in London, ripe and ready to avenge themselves upon our devoted cranium, which, although hardened throughout its ligneous formation by many blows, would not be proof against their united efforts. And we scarcely know how or where to begin. The instincts and different phases, under which this interesting race appears, are so numerous, that far from complaining of the paucity of materials we have to work upon, we are overwhelmed by mental suggestions, and rapidly-dissolving views, of the various classes from Guy's to the London University, from St. George's to the London Hospital, perpetually crowding upon our brains (if we have any), and rendering our ideas as completely muddled as those of a "new man" who has, for the first week of October, attended every single lecture in the day, from the commencement of chemistry, at nine in the morning, to the close of surgery, at eight in the evening. Lecture! auspicious word! we have a beginning prompted by the mere sound. We will address you, medical students, according to the style you are most accustomed to. Gentlemen,--Your attention is to be this morning directed to an important part of your course on physiology, which your various professors, at two o'clock on Saturday afternoon, will separately tell you is derived from two Greek words, so that we have no occasion to explain its meaning at present. Magendie, Mueller, Mayo, Millengen, and various other M's, have written works upon physiology, affecting the human race generally; you are now requested to listen to the demonstration of one species in particular--the Medical Student of London. Lay aside your deeper studies, then, and turn for a while to our lighter sketches; forget the globules of the blood in the contemplation of red billiard balls; supplant the _tunica arachnoidea_ of the brain by a gossamer hat--the _rete mucosum_ of the skin by a pea-jacket; the vital fluid by a pot of half-and-half. Call into play the flexor muscles of your arms with boxing-gloves and single-sticks; examine the secreting glands in the shape of kidneys and sweetbreads; demonstrate other theories connected with the human economy in an equally analogous and pleasant manner; lay aside your crib Celsus and Steggall's Manual for our own more enticing pages, and find your various habits therein reflected upon paper, with a truth to nature only exceeded by the artificial man of the same material in the Museum of King's College. Assume for a time all this joyousness. PUNCH has entered as a pupil at a medical school (he is not at liberty to say which), on purpose to note your propensities, and requests you for a short period to look upon him as one of your own lot. His course will commence next week, and "The New Man" will be the subject. [Illustration]