Gen. McClullan h;xs issued the follow ing order : First - Tlie attention of brigados and regimen+al (Jommissaries of Subsistence, and of officcrs acting as such, is directed to paragraphs 20, 21 and 22 of Subsistance Ilcguhitions, or paragraphs 1,073, 1,074 nnd 1,075 of thc Array Itegulations of 1S57. Subsistence officers must makc issues to the hospital, aod keep the accounts of hospital funda in striet conformity with tlio requircmcjts of the regulntions cited. Second - All changos of the station of medical oflicers to be promptly reported to tho Medicil Director at theso headquarterR, and the nuthority given by whieh tho chango was made. Third - Lcavcs of absence to medical officers uro prohibited únicas granted at these headquarters Fourlh - Patienls will not besent from the regimcntnl to thc general hospitals without tho nuthority of the Medical Director. Applications for this authority must bc made in writing, with the names and diseases of tho pntients, and bo handcd into tho offico of tho Medical Director bctwecn tho hours of nine and ton A. H. Fifth - TVhen a soldier is sent to tho general hospital his cornpany commandcr ehall certif}' and send with him his dogcriptive list and account of pay and clothing. Sixlh - Malo nurses and eooks for tho general hospitals aro to be detailed from tho privatcs of the army, regular and voluntccr. The allowanco will bo ono nurse to ten patients nnd one cook to fhirty. Wherc ffomen are cmployed tho nuniber of men to be callod for will not exceed a uumber sufficient to mike upjtho wholc force to the allowancc above authorized. Ilired nurses and cooks will be forthwith discharged. Seventh - Men roported at tho general hospitals for duty will bo sent by the surgeon in charge to the office of thc Medical Director at 10 o'clock, A. M., for the passes necessary to cnablo thein to rejnin their regimenté, FJijMli - Medical ofiieers joining this army, with or without troops, will report promptly to tho Medical Director in person. I f with troops, they will report tho uumber of men, the state of their supplies and the ambulance transportntion. Ninlh - Ambulances will not bo used for any othcr than tho specific purpose for which they are designed, viz : The transportation of the sick and wounded, except by the written authority of the brigr.do commander, the Medical Director of the army, and the Quartermaster in chargo-of them in tho city of Washington. Tho Provost Marshal .is directed to see that the provisions of this order are carried out, and will arrest every officer and confine every private and noncommissioned officer who is found violating it. All government ambulances now in possession of regimenté or separate corps will be turncd in to the chief Quartermaster, with the exception of onc twowhceled ambulance to each regiment. - One two wheeled transport cart will bo allowcd to each general hospital for tho convoyanco of marketing and hospital stores. Tenlh - The practico of bringing communications in person to the officers at ilicir headquarters, with a view to obtain immediatc attention to tho matter involved, proves a serious hindrance to tho prompt transaction of business, and must be discontinued. Unless undcr eitraordinary circumstances, all Communications for the General commanding are to be transmitted to his hoadquarters by the ordinary modes; and the person concerned will await replies to b) furnished them in the same manner. JUcvcnth - Persons having official business at theso headquarters will transact tho same between the hours of nine A. M. and tbree P. M. Twelfth - Thc srms of the troops must be thoroughly inspectcd by the company officers at least once a day. Thirteenih - The reveille will not be beatón until aftcr sutirisc, and hot coffee will be issued to the troops immcdiatcly after the reveille roll cali, as a preventativc of the effects of malaria. Foiirleadk - Troops on the march or changing positions will move without music. Drums are not to be beaten, nor trumpet sounded, exeept for the stated exercise and calis. l'ifteenth - All requisitions for ordnanco and ordnance stores and supplies f.jr the troops serving in this army will be transmitted througíi the appropriate commanders to the eilief of ordnance at their hcadquarters. Sixtcenth - Officors belonging to this army aro directed to wcar their uniforms at all times at their stations. Heventeenth - The small fort near Fort Corcoran, thrown up by tho Fourth Regiment Michigan Volun teers, will be known as Fort Woodbury. By command of Major-General McClellan. S. WILLIAMS, Ass't Adj-Gen'l. IlioiiARD B. Irwin, Aid-de-Camp.