As a general rule it would seem, as is natural, that the ratio of sick is inversely as the military age of the men. When a departure from this rule is perceived, as it will be in certain brigades, one important reason for it will probably be found in the lax and inefficient discipline of the regiment. I called attention to an instance of that sort a few days since, and was told that the regiment was demoralized from the inefficiency of the officers.

I ask attention in this place to a letter I have received from Brigadier-General Peck, a copy of which I inclose to show how much may be done by attention to certain sanitary measures that I have frequently suggested, and which have been more than once directed from your office. If officers could be imprisoned with the necessity of such measures, and convinced of their certain beneficial results, I feel sure they would all be zealous in enforcing them.

I am gratified to be able to state that typhoid fever, which I feared would seriously increase with the cold weather, has been much decreased in a very great majority of the regiments, and upon the whole I think I am justified in saying that the sanitary condition of this army is very satisfactory.

I take this occasion to say that I have sent an inspector of hospitals to Lander's division, and that as soon as the inspections of Alexander's and Duane's commands are completed, I shall send another to Parryville, Md., where I have just learned that typhoid fever has appeared and is increasing in one of the regular regiments stationed at that point.

Very respectfully, your obedient servant,

CHAS. S. TRIPLER,

Surgeon and Medical Director Army of the Potomac.

[Inclosure Numbers 1.]

STONE'S DIVISION.

Brigade Mean Total sick Percentage Brigade

and strength strength

regiment

GORMAN'S

BRIGADE

First 960 32 3.33 ..

Minnesota

Second New 832 30 3.60 1,792

York State

Militia

COLONEL

GROSVENOR

Seventh 990 20 2.02 ..

Michigan

Twentieth 637 30 4.71 ..

Massachuse

tts

Andrew 639 71 11.11 2,266

Sharpshoot

ers

BURNS'

BRIGADE

Sixty- 952 29 3.41 ..

ninth

Pennsylvan

ia

Seventy- 1,129 26 2.30 ..

first

Pennsylvan

ia

Seventy- 1,415 50 3.53 ..

second

Pennsylvan

ia

One 1,036 15 1.45 ..

hundred

and sixth

Pennsylvan

ia

Light 585 23 3.93 51.17

artillery

Tammany 803 54 6.72 ..

Forty-

second New

York

Fifteenth 809 68 8.40 ..

Massachuse

tts

Van Alen 860 23 2.67 ..

Cavalry

Company I, 150 6 4.00 2,622

First

Artillery

Brigade Bridge Division Division Divisi Division

and sick percenta strength on percenta

regiment ge sick ge

GORMAN'S

BRIGADE

First .. .. .. .. ..

Minnesota

Second New 62 3.46 .. .. ..

York State

Militia

COLONEL

GROSVENOR

Seventh .. .. .. .. ..

Michigan

Twentieth .. .. .. .. ..

Massachuse

tts

Andrew 121 5.34 .. .. ..

Sharpshoot

ers

BURNS'

BRIGADE

Sixty- .. .. .. .. ..

ninth

Pennsylvan

ia

Seventy- .. .. .. .. ..

first

Pennsylvan

ia

Seventy- .. .. .. .. ..

second

Pennsylvan

ia

One .. .. .. .. ..

hundred

and sixth

Pennsylvan

ia

Light 143 2.79 .. .. ..

artillery

Tammany .. .. .. .. ..

Forty-

second New

York

Fifteenth .. .. .. .. ..

Massachuse

tts

Van Alen .. .. .. .. ..

Cavalry

Company I, 151 5.75 11,797 477 4.04

First

Artillery